Hello Alan (aka M-38)...
If you have a copy of R. Gibson's book, the Krieghoff Parabellum, on pages 27 to 33; there is a good "features" comparison amongst frames made by DWM, Mauser, Simpson, and Kreighoff.
If your frame is not of Erfurt-make, you might find a clue as to which manufacturer made your frame by comparing your frame with the photos and descriptions of the "typical" features of the other luger manufacturers.
Hope this helps... <img src="graemlins/yltype.gif" border="0" alt="[typing]" />