Proof marks onGrip Screws

[barr44]

I have a DWM double date luger which is double dated 1918/1920.
The pistol was at some time worked on at the Ulm factory since is has the antler mark on the frame. The pistol has proof marks on the grip screws, a Crown over a U it looks like, which I believe is a firing proof, not sure. Would the Ulm factory people have proofed the grip screws after their repair, and would the double date been added at the ULM factory repair?
I have never encountered proof marks on any of the grip screws on any of my other Lugers, so just wondering why they would proof mark the grip screws after a repair. Did they have some type of indicator as to what repair was done when repairs were done?

[Roadster 02]

Grip screws are from an Erfurt Luger, they marked most parts

[Doubs]

Originally Posted by Roadster 02

Grip screws are from an Erfurt Luger, they marked most parts

They would also be from 1910 - 1914 as 1914 is the final year that Erfurt marked grip screws. Erfurt made no Lugers in 1915 and when they resumed production in 1916, grip screws were not marked.