In my strange and weird obsession with Lyman 310 tool, I have accumulated three .311 expanders, one screwed into a 303 Brit die body and the other two in 30-40 die bodies. However they are not the same.
Note how short the expander is in the middle plug and how the numbers are hand stamped one by one while the other two longer expanders have the numbers gang stamped.
Any guesses as to the difference. I have a theory, but it is just a theory with no facts to back it up.