Cliff,
The folks at FGS have a 1917/1920 double date arty in 95% ORIGINAL finish for an asking price of $ 2850.
It is the 4th. one down on this FGS web site page :
http://www.fgsinc.8m.com/photo_2.html
As yours might be a Weimar-period re-do, I think that would lower your gun's value somewhat...i.e. not having the original Imperial-era factory finish.
My WAG on price...$ 2250 or so...(others can tell me I am all wrong...)...if your gun is all factory original finish, then maybe $ 2500 or so...???
If your gun has some "bubba" re-bluing, then down to $ 1500-1600 or so.