I am not a serious collector, but have acquired a number of Stanley 750 and 720 chisels over the years. I have two 3/4″ 750 chisels. One is much newer or at least in much better shape than the other. Neither have had mushroomed or ground sockets. The newer one has an obviously  larger socket, say 1/8″ of more larger in diameter than the other. All else, blade size etc. appears equal.

Can anyone tell me what year the size of the sockets were changed on these chisels?

Thanks in advance.