Texasjack,
I live 22 miles north of Auburn on US 431. You seem to be a little disturbed that the caliber of your gun is not marked as 7x57R; at the time they were not marked as to nominal caliber, only bore diameter(not groove or bullet dia)and case length(not if it was rimmed or not). Also this marking was done by the proofhouse, not maker.This often causes confusion; as an example, both 8x57IR and 8x57R/360 would be marked 7.8/57,even though they are very different cartridges. Also it can be very confusing to compare different dimensions of cartridges without knowing where thay came from, the differences cited above are so small as to be insignifcant.If you look at the dimensions of the same cartridge, from different sources,you may see similar differences.This happens when cartridge dimensions are given in one and chamber dimensions in another(ie measureing a cartridge vs chamber cast), to say nothing of differences in tolerances or outright mistakes in measuring.The 7x57R is simply the 7x57 with a rim added, and loaded to lower pressure in deference to the actions used with the rimmed cartridge.In case you couldn't tell,7x57R is one of my favorites.
Mike
AU, Class of 67