This will now confuse you:
Believe it or not there really was a 7.65x54R way back..at least according to this listing as a musket.http://www.collectorsfirearms.com/admin ... emID=29950
But the 7.65x54R is not the same thing. Argie Mauser ammo IS NOT rimmed. Not sure why the Russians still use a rimmed large calibers in 7.62x54R today.
The 7.65x53 Mauser cartridge was adopted by the Belgian military around 1889, so the 7.65x53 is commonly known as the 7.65 Belgian Mauser. Shortly thereafter the 7.65x53 was adopted by several South American countries, including Argentina, so it is also known as the 7.65mm Argentine, particularly in North America. They are supposed to be the same cartridge, since they measure between 53 mm and 54 mm...some makers rounded the designation up to 54 !
Boxes are marked usually
7.65 x 54
7.65 x 53 Belgian