Plaintiff appeals from a judgment holding invalid J. E. Green et al. Patent No. 2,975,263, a patent on a method of making metallic honeycomb core. The purpose of the core is to maintain the surface sheets of panels used in aircraft and missiles in a spaced relationship with each other. The district court held that the prior art did not teach plaintiff’s claimed method but that by reason of the plaintiff’s sales of honeycomb core the rights to a patent on the process were lost under Section 102(b), Title 35 U.S.C.

All the questions in this appeal revolve around two methods of producing honeycomb core — the flat-pack method and the preformed or pre-expanded method.

Honeycomb core produced by either method looks like this:

The text of the application for the patent, filed July 6, 1954, was almost exclusively devoted to the flat-pack method and described a process which appellant’s brief fairly summarizes as follows:

The subsequent steps of the flat-pack method entailed the removal of the lower set of electrodes and its placement on the upper welded sheet of foil and the disposition of successive sheets of foil on the uppermost electrode. The successive sheets were then welded by the use of the welding gun. After the welding was completed, the pack of welded foil was expanded to form the cells of the honeycomb core.”

Except that Figure 6 (Figure 6 of the patent application) shown above depicts the core produced by either method (the pins 35 would not be shown in a drawing relating to the preform method), the drawings in the patent relate solely to the flat-pack method and illustrate it as follows:

Figure 3 (Figure 3 of the patent application) shows the flat foil (No. 16), the fingers (No. 21), the welding gun (No. 28) and the seam welds (No. 17). The drawings here copied do not show it, but the fingers are inter-connected to form what is referred to as a comb. It is clear from the text and the drawings that the structure must be expanded after the welding. This is explained in the patent application:

The only reference in the original application to the preformed method was this:

After three years of the usual sparring around in the patent office, plaintiff, in June, 1957, cancelled all claims which at that time remained in the application, and for the purpose of interference copied two claims from the previously granted Wasilisin Patent No. 2,780,716. The effect of this was to abandon all claims relating to the flat-pack method and to rely entirely upon a method using pre-formed foil.

Claim No. 1 of the plaintiff’s patent as finally allowed discloses this method and is as follows:

The claims copied from Wasilisin were held to be prior to Wasilisin by the Board of Patent Interference.

That there are differences in the two methods of producing honeycomb core is irrefragable. The one method uses flat foil, employs relatively flat fingers, requires pressure from the welding wheel to bend an upper foil to meet a lower one, and requires a mechanical step of expansion. The other method uses pre-corrugated foil, square fingers, requires no pressure to bring the area to be welded together, and eliminates the expansion step. The pre-formed method lends itself more readily to automation and produces a more uniform core.

The District Court concluded that the Green patent 2,975,263 was invalid because directed to a subject matter in public use more than one year prior to the filing of the application. This conclusion was based on these findings:

There is sufficient evidence to support Findings Nos. XII and XIII and Finding No. XI to the extent that that finding relates to the flat-pack method. There were no sales of core produced by the pre-formed method made more than one year prior to the filing date of July 6, 1954.

The record fairly shows that during the period of 1952, 1953 and 1954 the use of welded stainless steel honeycomb core was relatively new. Major aircraft producers were testing it and experimenting with machines to produce it. During this period standards were being developed for the core. Plaintiff using the flat-pack method prior to June, 1953 produced and filled at least four separate orders for core. The money value of the core definitely shown to have been sold was not great, somewhere between five and six hundred dollars. Some core produced by the flat-pack method was given away. It is probable that most, if not all, of the core sold and given away was used by the purchasers for test and experimental purposes, but certainly plaintiff put no limitation on the use to be made of it. The sales of core were sufficient to put the flat-pack method into public use and we cannot say on the record that the District Court erred in not finding the use experimental.

Having in mind the differences in material used, the steps of production, the adaptability to automation, and the finished product, did the sales of the core produced by the flat-pack method put the pre-formed method in public use? The guide lines, so far established are these: One sale or gift of an article is sufficient to constitute a sale or public use. Where an article is sold the use is public even though the invention be hidden physically or chemically as a part of a larger article. Likewise where an article is sold, there is a sale or public use of the article itself and of all improvements on the thing which would be obvious to one skilled in the art. The holding in Stauffer v. Slenderella Systems of California, 254 F.2d 127 (9th Cir. 1957), relied upon by appellant is not contrary. See footnote 2, page 128, and the next to the last paragraph at page 130. The language in the opinion appearing to be to the contrary is dictum, and not necessary to the holding of the case.

Where a process patent is involved and there is a sale of a product of the process, such is a public use of the process if the product sold discloses the process, or even if it does not.

None of these rules quite compel a result here — here there was no sale within the meaning of § 102(b) of the pre-formed core as such, nor was there under any view of the evidence a public use of the exact method patented because, as indicated, the flat-pack method was abandoned in the patent office and the patent issued on claims describing the pre-formed method.

On the facts, the case which most nearly resembles this one is Smith & Griggs Mfg. Co. v. Sprague, 123 U.S. 249 , 8 S.Ct. 122 , 31 L.Ed. 141 (1887) where the court determined that the sale of a product made by a machine not identical with the one patented constituted a public use. There the patent covered a machine for making levers for boot buckles. The basic machine was used by the inventor in his own established business, and during a period of three years between 1874 and 1877 he made some 7,000,000 buckle levers with it. There was no real effort to keep the use of the machine secret. Within a year prior to the application for a patent the inventor made changes of which the court said:

The court finally concluded that the use was not experimental and that .the patentee had therefore unduly delayed filing his patent application. We deduce from this case that not every improvement is sufficient to take a prior invention out of the operation of Section 102(b). The question then is — what degree of improvement is necessary?

If the purpose of 102(b) is to prevent an inventor from combining a period of monopoly resulting from a public exploitation of a secret use with the period of monopoly protection afforded by the patent, then we see no reason for devising a different test for a process used than for an article sold or a publication made. In either case the invention should fall within 102(b) if the differences between the claimed thing and the sold or used thing are obvious to one skilled in the art. In either case unless the improvements would be patentable, the inventor has used or disclosed his invention contrary to the purpose of Section 102(b).

We agree with the district court that the process was in public use. Whether one method or two be involved and whether we treat the question as one of fact or law, the differences between the flat-pack method and the pre-formed method did not amount to an invention.

Once the flat-pack method is disclosed, we think that the appearance of the completed core in itself suggests to one skilled in the art the use of pre-corrugated foil. After such suggestion the shape of the fingers is dictated by the shape of the corrugation. The requirements for pressure on the welding wheel and an expansion step simply disappear.

Hence we hold that the sales of core made by the flat-pack method constituted a public use of the pre-formed method and that under Section 102(b) the Green ’263 patent is invalid. The judgment is affirmed.

. The word “plaintiff” will be used to designate plaintiff and its predecessors. . “A person shall be entitled to a patent unless * * * (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. * * * ” 35 U.S.C. § 102 . . pp. 13-14 of Appellant’s Brief. . P. 3, lines 11-18 of the letters patent No. 2,975,263. . P. 3, lines 26-30 of the letters patent No. 2,975,263. . Smith & Griggs Mfg. Co. v. Sprague, 123 U.S. 249 , 8 S.Ct. 122 , 31 L.Ed. 141 (1887). . Egbert v. Lippman, 104 U.S. 333 , 26 L. Ed. 755 (1881); Hall v. Macneale, 107 U.S. 90 , 2 S.Ct. 73 , 27 L.Ed. 367 (1882); Metallizing Engineering Co. v. Kenyon Bearing and A. P. Co., 2 Cir. 1946, 153 F.2d 516 , cert. denied, 328 U.S. 840 , 66 S.Ct. 1016 , 90 L.Ed. 1615 (1946). . International Tooth Crown Company v. Gaylord, 140 U.S. 55 , 11 S.Ct. 716 , 35 L.Ed. 347 (1891). See Dix-Seal Corporation v. New Haven Trap Rock Co., D. Conn.1964, 236 F.Supp. 914 , for an able discussion of the problem. . Soffron v. S. W. Lovell & Company, Cir. 1, 1957, 246 F.2d 769 . . Metallizing Engineering Co. v. Kenyon Bearing & Auto Parts Co., supra, note 7; Conmar Products Corp. v. Universal Slide Fastener Co., 2 Cir. 1949, 172 F.2d 150 ; U. S. Chemical Corporation v. Plastic Glass Corp., 3 Cir. 1957, 243 F.2d 892 , cert. denied, 355 U.S. 836 , 78 S.Ct. 59 , 2 L.Ed.2d 47 . . Smith & Griggs Mfg. Co. v. Sprague, supra, 123 U.S. at p. 265 , 8 S.Ct. 122 . . Metallizing Engineering Co. v. Kenyon Bearing & Auto Parts Co., supra, note 7, 153 F.2d at p. 520 . . The prior art suggests the use of precorrugated metal. Smith (2,324,435) and Partiot (2,445,801) patents. . At one stage plaintiff seems to have been in agreement. In plaintiff’s closing brief in the interference proceeding, it was urged: Therefore it is readily apparent that Green et al, [plaintiff’s predecessor], the senior party, rely on the entire disclosure of the application including the specification and the drawings [the drawings except for Figure 6 related to the flat-pack method] to support their right to make the two counts of the interference [both referring to the preform method] and it is readily apparent to one shilled in the art hoio the teachings of the method would he applied to the manufacture of preformed core utilizing sections of corrugated metal foil. (Emphasis added)