After a certain amount of die abrading and repair, those serifs invariably get polished off leaving that left leg straight up and down.
To repeat, the R in LIBERTY on your typical Eisenhower Dollar has serifs on the left leg of that R. Here's a little post although it does not concentrate specifically on the 1971-S Pegleg Proof it does give some definition on what a pegleg is. It is kinda weird that the post went unanswered after a couple of years!
