My 60's PL10 Peugeot has two centerpunch indentations on the bottom side-edge of BB where deformation appears to secure fixed-cup flat. I don't know if this is factory or was subsequently performed during service. I'd be interested if anyone else may have seen this on their bikes, Peugeot or otherwise. Nowadays, I would think Locktite might be a better method...but knowing these cups can sometimes be a b to get off...maybe not.
Jack Romans
Sacramento, CAlifornia