The one pictured in your 2nd post is by Dominion Cartridge Co. of Canada. Seems they had trouble with the headstamp bunter’s D & the top of the “D” got filled in, so now appears something like a “U”. This is actually common of a number of case types in their product line, as with and without this ‘flaw’ was sold to the public.
United States Cartridge Co. variations are headstamped “U.S.C.Co.”
The Western “Oswald” headstamp is " WCC [over] 6.5 m/m " note the lack of a “Co.” & it would be a round nosed full metal jacketed bullet (FMJ). Also the “Oswald” is for the Italian Carcano & not for use in a Mann. Scho.
Soft nosed bullets are generally considered sporting as sometimes are FMJ. If the military use a round is generally FMJ & the headstamp would reflect the country, arsenal & such. The Mann Scho. is found in military loadings as it was adopted by the Greeks.
For a start you might want to study the link concerning headstamps found on this site.