Firstly, working from first principles:
The clip holds 6 rounds
Therefore, which 6 round magazine rifles are there? (or 12 round?)
M91 Carcano and M1889/1911/1931 Schmidt Rubin.
Eliminate 6,5 Carcano, as this clip is asymmetrical…The Carcano clip is symmetrical, and if a 7,62 Cartridge is loose, the smaller bodied 6,5 Carcano will be even looser. it also eliminates any other cartridge(experimental or service issue), with diameter equal to or smaller than the 7,62 Nato.
Fact: 6x 7,62 cartridges fit in clip, but loosely;
Therefore the proper cartridge for this clip must be of greater diameter than the 7,62 Nato, ie, greated than .470 inch.
Candidates greater than .470 (and rimless) are the French MAS Rifle cartridge (M24/29) at .485 inch, and the Swiss M1911 cartridge ( at .495 )
The French rifle is eliminated, as it is 5 round stripper fed (5 shot mag for Bolt guns, 10-round mag for Semi-Autos.
That leaves the Swiss rifles>
The swiss had used a 6 round stripper clip, made of cardboard and tinplate, from the 1889 model onwards. The Clip allowes the cartridges to be held by the body of the clip, looks like a “packet or En-Bloc” desing, when in reality, it serves to guide the cartridges into a double column magazine, of 12 (M1889) or 6 (M1911 & M31) round capacity.
The markings seem to denote a change in type…there is a “F” overstamped or cancelled followed by a “G”, a series of experimental prototypes?
I doubt very much that RSA stands for “Republic of South Africa”…In fact the initials probably represent a company or establishement in Switzerland.
My other indications that this is not an “enbloc” clip but a Stripper, is that there are no obvious “Latch Points” for an “enbloc” (such as the pressed out bridge on a Carcano or other “Mannlicher” style clips, or pressed slots in the Garand Clip.
My suggestion is to try fitting 6 of 7,5 Swiss cases ( or failing that, 6 pieces of 1/2 inch dowel) to check the fit.
Maybe some of our Swiss colleagues could be of assistance?
PS, If I remember correctly that the StG57 of Switzerland has a 24 round mag ( 4x6), and this clip could be an improvement to be used with the StG, rather than the S-R series of rifles???
regards, Doc AV