Hello,
This topic is very interesting and tricky as well.
I would like only adding a piece to this puzzle.
In the picture attached a copy of an original Bayer document where the LP08 delivery is described. This document covers the period from August 1st 1915 up to March 10th 1915.
As you can see the Erfurt Arsenal had delivered LP08 during 1915. I guess that these pistols were dated 1914 because of, right now, no pistols are found dated 1915.
It means that the Erfurt LP08 stock was enough for cover a part of 1915 deliveries.
Cio