What kind of Luger is this?

[cokerkbc]

I have just aquired a very nice(98% condition) luger. the top of the chamber says 1921, it is of DWM manufacture, all matching #'s, ser. no. 83XXX with a cursive a, stock lug on backstrap, stamped on frontstrap is O.P.M. 3.1.2., wood checkered grips, magazine with plastic bottom and marked fxo with a eagle and 37 under it. any help would be appreciated.