Yup; police Luger, both safeties; mag safety mutilated. The 1920 on the chamber is a gov't property mark, no relation to year. Serial number looks like
6720 (can't see if there's a suffix). Yes to DWM toggle, I don't know enough to say if the frame is matching.
Refinished it's worth about $700 - $900 to Joe Average-gun-show-browser-with-cash. Most collectors don''t bother with refinished Lugers, except as 'shooters'.
A good 'shooter' for a start to your collection...