1937 Mauser S/42 Luger straw part question

[mikearc99]

Here is a 1937 Luger s/42 in serial 7661X .The only straw part is the Ejector and the safety bar is somewhat blued with some white still showing and also the trigger bar assembly does not have a last 2 numbers of the serial. Any info about this Luger if why only the straw part is the ejector but not the trigger, takedown level. Is the serial number range supposed to when Mauser switched to bluing the small parts