Why was the "X" marked on RC / VoPo Lugers?

[mrerick]

While I think I know the reason, I have yet to find any factual evidence as to why the "X" was stamped on Russian Capture (RC) and Volkspolizei (VoPo) Lugers.

I can think of two logical explanations.

The first (which I think is most likely) is similar to the logic behind the Weimar "1920" property mark. Everything after the war that was captured or turned in to the Russians got marked to prevent the gun being turned in a second time for a reward, and to indicate that it now was Russian property.

The second explanation is that the large "X" was added after the firearm had been through the Russian rework program.

Does anyone have a factual source to confirm why the large "X" was stamped on these guns? At a minimum Lugers and K98 rifles have this mark.

Thanks, Marc