Ronchard Cizeron in the 1890's began stamping his barrels "Acier Comprime" which was a direct translation of the Whitworth steel "Compressed Steel" mark.
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https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=557199&page=4Whitworth steel barrels appeared in 1875:
Whitworth fluid compressed steel was invented by Mr. Joseph Whitworth, who we already talked about when discussing polygonal bore rifling and the Whitworth rifle. Mr. Whitworth was the eminent mechanical engineer of his day and came up with a way of producing a stronger cast steel. His process consists of melting a steel ingot into a mold and applying pressure of up to 6 tons/sq. inch to the mold while the steel is in a liquid state. The pressure drives out all the gases and eliminates blowholes in the cast steel. It also increases the density and strength of the steel. According to W.W. Greener's book, The Gun and its Development, with the introduction of choke boring in shotgun barrels, whitworth steel was found very suitable for this process and started replacing damascus barrels, and he mentions in 1875, "Whitworth steel was giving great satisfaction for rifle barrels, a leading London gun-maker adopted it for shotgun barrels." The leading London gun-maker was Purdey & Sons, who used Whitworth steel exclusively for years after that. Use of Whitworth steel for gun-making spread to America as well and well known makers such as Parker, L.C. Smith and Lefevre were making guns using this steel, way into the 1930s.
This DGS line discussed it in 2007...Whitworth patented his compressed steel in 1874; 1st Purdey with Whitworth barrels delivered 1 Jan 1880, ordered 3 years previously.
https://www.doublegunshop.com/forums/ubb...&PHPSESSID=Salut Argo44
Jean Didier était le fils de Jean-Pierre Didier et de Marie Drevet. Il est né à Saint-Etienne le 9 septembre 1856. épouse à Saint-Etienne le 25 novembre 1882, Fleurine Mathaud (Saint-Etienne, 4 août 1859), couturière 7 rue du Haut Vernay. Jean Didier est alors canonnier 5 rue du Haut Vernay. En 1883, il est canonnier au 14 de la rue du Haut Vernay et en 1888, au 11 Grande rue Saint-Roch. Associé à la veuve de Ronchard-Cizeron par acte du 22 juillet 1901, il fonde la société Didier et Cie, dans laquelle la veuve Ronchard-Cizeron est majoritaire. Ils déposent les marques « déposé - acier comprimé » au-dessus et au-dessous d'une presse le 12 août 1904 et « RC rectifié » de part et d'autre et au-dessous d'une médaille le 28 novembre 1907. Didier et Cie, rassemblant les ateliers et les marques de Didier-Drevet et Ronchard-Cizeron, sont hors-concours comme membre du jury à Saint-Etienne en 1904, à Liège en 1905, primés à Londres en 1908, à Bruxelles en 1910 et à Turin en 1911. Didier et Cie obtiennent également la médaille d'or du prix Escoffier de la Chambre de commerce en 1904 pour leur canon plume « Euréka » et sa cale unique en acier mandriné, breveté
Il décède à Saint-Etienne en décembre 1940.
