http://imgur.com/a/SlHzA All it says is "Lager 7864".
If anyone is interested in the content: http://www.reddit.com/r/pics/comments/369o77/during_my_grandfathers_imprisonment_in_a_soviet/
This page says it was near Moscow, I'll see what else I can find about it, it could've been moved during the later stages of the war, when the number of PoWs increased.
Upd: yep, near Moscow: http://i.imgur.com/3tgeAjL.jpg
Upd2: have you tried to contact http://www.drk-suchdienst.org/ ? They might've more info, being German Red Cross.
The Russian at the top says Union of the Red Cross and Red Crescent, and below POW mail. Unfortunately I don't see any other useful info in Russian.
