As detailed in Jan Still's excellent "Third Reich Lugers" Mauser began extending the rear frame to better contain the rear axle toggle pin, the one that connects the toggle train to the receiver. Earlier Navy Models had solved the same perceived potential problem with an enlarged head on this pin. My question, is why did Mauser go to the trouble to mill out the section under the pin to form what collecters term as the Mauser hump. G Date Lugers were not done this way, at least all the ones I have seen, but some eariler K date Lugers were. After this milling practice was resumed, after the G dates, it was used on all subsequent Mauser Lugers. It just seems like a wasted effort to me. I have not seen yet any documentation saying why this was done by the factory. Both G dates without the hump and later ones with the hump certainly function the same way. Any ideas on why this was done? Thanks! ~Thor~

My guess is that there may have been a very few reported problems with the G dates, Thor. In an attempt to simplify the machining process for greater mass production, they may have created an error, that was subsequently remedied after the G dates.
Perhaps documentation was lost on this, but it seems unlikely that a "solution" would have been re-instituted for a non existing problem.
Since this was the era of the "sneak" Lugers, maybe the reported problems factory paperwork may have been lost, misplaced, or destroyed.
The old saying "don't fix it if it ain't broke" springs to mind.
Just a hypothesis, of course, but that would be my guess.