Kingfisher:
Welcome. We would appreciate a first name and a general location!
Here is a short thread on the other forum with a similar gun:
http://luger.gunboards.com/showthread.php?t=15366
Looks like the rework dates from the 1940s. Any way you could get us some photos? You mentioned the chamber is blank, but is the toggle marked with either "DWM" or "Erfurt"?
Clark