aside from having engraved markings, rigby .275,s were also designated I AND II and this was done with a silver lettering on the bottom metal just ahead of the bullet release hole I was for standard velocity bullet weight 175 ,,II was for high velocity 140 grain bullet .
my rigby is sighted for the 175 grain bullet its marked with the I ,there are no other markings
outside of oberndorf on the side rail the ring has a V sideways and the serial number ,the barrel is not visibly marked with a caliber , above the woodline only is the rigby address. my 303. and 400/350 have stories to tell on the recievers !!.....paul