Mauser's Rear Frame "Bump"...?

Can anyone let me know when Mauser started building the rear frame "bump" to prevent the rear toggle link pin from falling out when the toggle assembly was in its full rear position ?


I have seen some Mauser S/42 coded lugers without this "bump".


Should this "bump" occur on all Mauser lugers, i.e. K-dates, G-dates, byf's, Banners, etc. ?


Appreciate any help...