I saw this Luger yesterday at a dealer. It's in poor condition but I thought that the safety was interesting. The letters are cyrillic but I'm not sure if this is Russian or Bulgarian. The toggle was a mismatched Simson & Co, Suhl example. There was no stock lug. Here are some photos:
http://boards.rennlist.com/lfupload/UnknownLeft.JPG
http://boards.rennlist.com/lfupload/CyrillicSafety.JPG
http://boards.rennlist.com/lfupload/UnknownRight.JPG
http://boards.rennlist.com/lfupload/UnknownToggle.JPG