Don't worry about the 3 1/4 Ton mark as that wasn't used until after 1954. The 1 1/4 ounce mark and 2 3/4" chamber is the same. Best to get European cartridges if possible and look for the CIP mark on the box. Details on the box will explain what guns they are suitable for. In fact you can use anything European for chamber lengths 2 3/4" or less but not those marked for 2 3/4" Magnum (usually 1 1/2 ounce loads). Nice looking gun by the way. Lagopus.....