Dymo Industries, Inc. herein appeals from two judgments rendered by the District Court for the Central District of California in related patent actions. The two suits were consolidated for trial concerning the validity of the patents in question. No. 21533 — an infringement action — was heard by the district court pursuant to 28 U.S.C. §§ 1338 (a), 1400 (b) (1964), and No. 21534 was a declaratory judgment action authorized by 28 U.S.C. § 2201 (1964). Our jurisdiction rests on 28 U.S.C. § 1291 (1964).

I. BACKGROUND OF THE APPEAL

Three patents are in issue, all of which were originally issued to D. W. Souza and are presently owned by Dymo. Each of the patents relates to an embossable plastic tape on which characters may be stamped to create what have become relatively familiar plastic labels. The labels may be produced individually and inexpensively by use of a hand embossing machine, and have therefore become rather widely used by small businesses and private individuals as well as by industry in general. The distinctive feature of the tapes is that, when they are embossed, the characters thus stamped upon them take on a white color, contrasting with the original dark shades of the plastics. This “stress-whitening” quality of the plastics used — which are described in the patent claims as polyvinyl chloride and copolymers of polyvinyl chloride, especially copolymers of vinyl chloride and vinyl acetate — renders the finished label particularly readable and attractive.

The patents in question are the following :

(a) No. 2,925,625, dated February 23, 1960, and entitled “Contrast Color Embossed Plastics and Method of Production.” This patent covers the method for producing the labels described above, and will be referred to as the “ ’625 patent” or the “method patent.”

(b) No. 2,996,822, dated August 22, 1961, and entitled “Contrast Color Embossed Plastics.” This patent has as its subject matter the plastic labels themselves, and will be referred to as the “ ’822 patent” or the “label patent.”

(c) No. 3,036,945, dated May 29, 1962, and entitled “Embossable Plastic Assembly.” The subject matter of this patent is a product marketed by Dymo and others consisting of three layers: (1) the tape described above, (2) a pressure-sensitive adhesive material, and (3) a removable backing. The assembly is constructed so that one can emboss the plastic, peel off the protective backing, and easily apply the resulting adhesive-backed label to the surface to which he desires to attach it. This patent will be referred to as the “ ’945 patent” or the “adhesive tape patent.”

Asserting that these patents (along with others not here in issue) had been infringed, Dymo brought suit in No. 21533 against Com-Tech, Inc., a maker of tapes similar to those described above, seeking damages and injunctive relief. Com-Tech denied infringement and pleaded the invalidity of all three patents. Avery Products Corporation, another manufacturer of embossable plastic tapes, then brought suit in No. 21534, seeking a declaration of its rights with respect to the products covered by the Dymo patents. Finding that an actual controversy existed in the latter action, the district court ordered the two suits consolidated for trial as to the patents’ invalidity. C.T. 1-2. After trial, the court rendered judgment against Dymo in each case, holding that the Dymo patents were invalid and that they had not been infringed by Com-Tech. In view of its conclusion with regard to invalidity, the court found further proceedings in No. 21534, dealing with the question of Avery’s possible infringement, to be unnecessary. It is from these judgments that Dymo now appeals.

The essential questions for our determination concern whether there is substantial evidence in the record to support the trial court’s findings, leading to its conclusions of law, that the Dymo patents are invalid because their subject matter (a) was anticipated by the prior art and therefore lacked the requisite novelty under 35 U.S.C. § 102 (a), (b) (1964), and (b) was rendered “obvious” by that prior art and therefore was unpatentable under 35 U.S.C. § 103 (1964).

II. ISSUANCE OF THE SOUZA PATENTS

The district court’s findings of fact relating to the issuance of the Dymo patents find full support in the record and are summarized in the discussion immediately following. D. W. Souza, to whom the patents in question were orginally issued, had been engaged in the radiator repair business prior to his involvement in the matters giving rise to these actions. In the course of his work he had hand-embossed metal tapes to produce radiator identification tags. Deciding that plastic might be used for such tags as well as metal, he procured from the Union Carbide Corporation sheets of various commercially available plastics. In hand-embossing them he noticed that on certain of the plastics the embossed characters were whitened, in contrast with the darker color background of the unembossed areas.

After further experimentation Souza applied for the patents here in question. The district court found that the prior art considered by the Patent Office took cognizance of the whitening effect upon which Souza’s applications were based, but did not utilize the effect to produce color-contrast writing. Even on the basis of this prior art, the Examiner in the prosecution file of the method patent at first rejected the claims, stating that

Souza prevailed over this initial rejection, however, by contending that his invention consisted essentially of the recognition of a desirable result (the production of color-contrast, embossed writing) from an effect (stress-whitening of certain plastics) which had previously been thought undesirable.

The district court found that the most pertinent prior art, however, was not before the Patent Office when it approved Souza’s applications, and that therefore the presumption of validity attaching to the method and label patents, 35 U.S.C. § 282 (Supp. II, 1967), was overcome:

and, as to prior knowledge and uses, activities, prior to the alleged invention by Souza, at Union Carbide Corporation, Addressograph-Multigraph Corporation, and Industrial Rayon Corporation.” C.T. 76-77, 143.

We turn now to an examination of this prior art, through a consideration of the district court’s findings relating thereto.

III. NOVELTY — METHOD AND LABEL PATENTS

A. The French Patent

Findings of fact 14, 15 and 16 read as follows:

Dymo challenges these findings by arguing specifically that Buschmann was unable to produce a color-contrasting sheet of plastic in accordance with the teaching of the French patent — and, more generally, that that patent was too indefinite and inaccurate to constitute an anticipation of the Souza method and label patents. We hold, however, that the record supports the district court’s finding with regard to Buschmann’s demonstration, and that the court’s conclusion as to anticipation was correct. Specifically in point is the testimony of Dr. Rodney Andrews, one of Avery’s expert witnesses, concerning the teaching of the French patent in comparison with aspects of Souza’s applications, R.T. 1000-14; that of Buschmann, to the effect that his demonstration work followed the teaching of the French patent, R.T. 1194-97; and a statement by Dr. Carl S. Miner, Jr., one of Dymo’s experts, to the same effect, R.T. 1971-72. See also R.T. 1257-58, Ex. IB. Furthermore, the trial court was hardly compelled as a matter of law to find that the color contrast produced by the method of the French patent differed in any significant fashion from that yielded by the Souza method patent. See Kalich v. Paterson Pac. Parchment Co., 137 F.2d 649, 652 (9th Cir. 1943) (citing rule that “one is not entitled to a patent who merely makes a change in form, proportion or degree”). The Souza patent does not, in fact, draw any distinction among degrees of “whitening.”

B. The Union Carbide Publications

Dymo argues that these publications did not sufficiently specify the plastics that could be stress-whitened, and that therefore they should not be held to constitute an anticipation of the method and label patents. We do not pass upon the district court’s conclusion with respect to the 1942 brochure, but as to the 1945 publication, we feel that the reference to “higher impact resisting” grades of Vinylite materials (described in the earlier brochure as col-polymers of vinyl chloride and vinyl acetate) may properly have been taken by the district court to have sufficiently specified the stress-sensitive plastics that will produce the effect Souza sought to patent. There was expert testimony to that effect. R.T. 477. We therefore find no fault with the court’s conclusion in regard to anticipation by that publication.

C. The German Publication “Kunstoffe in Technischen Korrosionsschutz, Handbuch fur Vinidur und Oppanol”

Finding of fact 20 of the district court is as follows:

Dymo’s argument with respect to anticipation by the German publication is essentially the same as that made in connection with the French patent and the Union Carbide publications: it contends that the publication does not specifically disclose the plastics to be used in obtaining stress-whitened labels. The publication does refer to a specific German plastic, Vinidur, which — according to at least one technical publication widely available long before the date of Souza’s patent applications — is a 'rigid, polyvinyl chloride plastic. Ex. HC, R.T. 894-99. That reference alone, however, is insufficient to render us as certain that there has been an anticipation as we are in regard to the French patent and the 1945 Union Carbide publication, and we do not pass upon the district court’s conclusion to that effect.

D. The Work of Myers and Bates

The district court also found that the previous work of two men, Clarence Myers and D. W. Bates, each constituted anticipation, as follows:

We neither affirm nor reject the district court’s conclusions as to anticipation by Myers and Bates. Myers’ work was closely related to the Union Carbide publications referred to above, and we need not discuss that work as a separate instance of anticipation. With regard to Bates’ work, we think the record supports the conclusion that stress-whitened credit cards were offered for sale by Addressograph to the Richfield Oil Corporation more than one year prior to Souza’s patent applications. Dymo admits that sample credit cards were made, and Hutchings testified that he and an Addressograph sales representative met several times with Richfield personnel regarding the possible sale to Richfield of such cards. R.T. 644-48. Furthermore, Bates himself deposed explicitly that the cards were offered for sale. R.T. 619-20. See also R.T. 582-583, 606, 649-659. A strong case is thus made for the proposition that the requirements of 35 U.S.C. § 102 (b) (1964) were not met with respect to the method and label patents. See Corona Cord Tire Co. v. Dovan Chem. Corp., 276 U.S. 358, 384-385 , 48 S.Ct. 380 , 72 L.Ed. 610 (1928); Monroe Auto Equipment Co. v. Heckethorn Mfg. & Supply Co., 332 F.2d 406, 416 (6th Cir.), cert. denied, 379 U.S. 888 , 85 S.Ct. 160 , 13 L.Ed.2d 93 (1964); Philco Corp. v. Admiral Corp., 199 F.Supp. 797, 815-818 (D.Del.1961). Dymo argues, however, that Bates’ work represents merely a series of abandoned experiments. And although that contention seems to us doubtful in view of the factual findings and authorities referred to above, it does draw at least some support from the Second Circuit’s decision in Lyon v. Bausch & Lomb Optical Co., 224 F.2d 530 , modified on rehearing, 106 U.S.P.Q. 240 , cert. denied, 350 U.S. 911 , 76 S.Ct. 193 , 100 L.Ed. 799 (1955) (L. Hand, J.), which held that there had been an “abandonment” (negating anticipatory sales and use) in somewhat similar circumstances. In view of the existence of several alternative grounds for affirming the district court’s decision, therefore, we decline to pass upon the question of anticipation by Bates.

E. The Leitz Folders

Dymo’s challenge to this finding is restricted to the contention that the Leitz folders were not in “public use” within the meaning of 35 U.S.C. § 102 (b) (1964), but rather were the objects of a “secret use.” It is clear, however, that the folders were not intentionally hidden by Industrial Rayon, as in the situations to which holdings of “secret usage” have been limited. See, e. g., Monolith Portland Midwest Co. v. Kaisar Aluminum & Chem. Corp., 267 F.Supp. 726, 783 (S.D.Cal.1966); E. W. Bliss Co. v. Southern Can Co., 251 F. 903 (D.Md.), aff’d, 265 F. 1018 (4th Cir. 1920). They were found to have been put to ordinary use, and such action is sufficient — where, as here, one skilled in the art would have recognized them as produced by a simple embossing process, R. T. 1043-44 — to constitute a “public use” rendering the Souza method and label patents invalid. Hall v. Macneale, 107 U.S. 90, 97 , 2 S.Ct. 73 , 27 L.Ed. 367 (1883).

IV. OBVIOUSNESS — METHOD AND LABEL PATENTS

Even if the instances of prior art relied upon are assumed arguendo to be insufficient to render the method and label patents anticipated, there can be no doubt (on the basis of the factual findings which the district court properly made) that they approached the subject matter of those patents so closely that whatever improvements Souza may have accomplished were obvious to one skilled in the art. The patents are therefore invalid under 35 U.S.C. § 103 (1964). See Sinclair & Carroll Co. v. Interchemical Corp., 325 U.S. 327, 335 , 65 S.Ct. 1143 , 89 L.Ed. 1644 (1945); Griffith Rubber Mills v. Hoffar, 313 F.2d 1, 3-4 (9th Cir. 1963); Walker v. General Motors Corp., 362 F.2d 56 , 60 n. 3 (9th Cir. 1966).

V. THE ADHESIVE TAPE PATENT

It is not seriously disputed that the only original aspect of the Souza adhesive tape patent lay in the supposed originality of the color-contrast label itself. The invalidity of the method and label patents, then, renders the adhesive tape patent also invalid, and the district court’s conclusion to that effect must be affirmed. C.T. 105-06, 162.

The district court also found with respect to the adhesive tape patent that:

This finding of fact to the effect that G. & S. Sales placed the subject matter of the adhesive tape patent on sale more than a year prior to the patent application is not clearly erroneous, and provides another foundation for the district court’s conclusion regarding that patent’s invalidity. Souza’s deposition reveals an affirmative response to the question whether certain of his activities prior to August 8, 1957, were in connection with the “sale of embossable plastic tapes having an adhesive backing,” with a “liner or protective backing on the adhesive.” R.T. 1439-40. Stafford testified to a similar effect. R.T. 1420. See also R.T. 1116-17, 1400-02, 1445-46, Exs. CH, CL, CW, KI. Dymo’s attempt to limit the subject matter of the patent to tape assemblies with ductile protective backings — polyethylene, for instance, rather than paper — cannot succeéd in view of general language of the patent claims themselves, which cover any assemblies with a “detachable protective backing” (claims 1, 2), or “detachable backing sheet layer” (claims 3, 4). Ex. 3. And testimony tending to show that early sales of the adhesive tape assembly were experimental might reasonably have been overcome in the district court’s weighing of the evidence by the contrary testimony referred to above.

It is true that Dymo has enjoyed considerable commercial success with the subject matter of the Souza patents. Success in the marketplace is, however, a secondary consideration in evaluating the validity of a patent under 35 U.S.C. §§ 102 , 103. See, e. g., Jeddeloh Bros. Sweed Mills, Inc. v. Coe Mfg. Co., 375 F.2d 85 , 92 (9th Cir.), cert. denied, 389 U.S. 823 , 88 S.Ct. 57 , 19 L.Ed.2d 76 (1967). Energetic promotion may make successful a product that has lingered in commercial limbo for years. The needs and attitudes of potential buyers often change, so that a product which did not meet with great demand in one year- — or decade — may be eagerly sought by customers in another. Dymo’s thriving business may well be the result of such factors. And, although it will not have a monopoly on the labels here in question, that business will no doubt continue to thrive. It is clear, however, that the subject matter of the Souza patents is not sufficiently novel — nor is it sufficiently “nonobvious”- — to merit a patent monopoly. The contributions of Souza and Dymo should not be denigrated ; but they do not rise to the level of invention. At most, they represent the rediscovery — and the very successful exploitation — of an idea which had been discovered several times before.

Since we affirm the district court’s conclusion that the three patents are invalid, we need not consider whether Com-Tech has infringed them.

Affirmed.

. Section 102 reads as follows: “A person shall be entitled to a patent unless— “(a) the invention was known or used by others in this country, or patented or described in a printed publication in this or a foreign country, before the invention thereof by the applicant for patent, or “(b) the invention was patented or described in a printed publication in this or a foreign country or in public use or on sale in this country, more than one year prior to the date of the application for patent in the United States * * . “A patent may not be obtained though the invention is not identically disclosed or described as set forth in section 102 of this title, if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art to which the subject matter pertains. * * *” . This quotation is taken from the district court’s findings of fact. The district judge set out separate findings of fact and conclusions of law in each case, although there is an almost total coincidenee between the two sets of findings. Parallel C.T. citations will therefore be supplied when we refer to those findings.