Detail Questions for the Experts

I notice there is a fat trigger and a slim trigger. The slim one seems to be used on Erfurt Lugers and on DWM 1908 Lugers and earlier. 1914 DWM Lugers and later, and Mauser Lugers seem to use the fat trigger. Is that correct so far and is there anything else to be known about triggers, such as the reason for the change?


I notice that firing pins are both fluted and unfluted, and I would guess the unfluted to be the earlier design. I suppose the grooves are to relieve gas pressure. When was this design change made?


I have Lugers at Random, Luger Tips, and Luger Handbook but none mention triggers or firing pins. I should probably get Sills' books but I just got those other three and my Luger book budget is used up for a while.