You show a 1912 mfg. DWM made P08; a military WWI luger taken into police service after the war.
The 1920 is a Weimar property marking; the S.Anh.4. is the police marking for the Schupo of Anhalt weapon #4.
There is much more info in the stickies.
With two different numbers mentioned the pistol may be mismatched, but the pictures are not good enough to tell and don't show the serial numbers on the barrel or frame front, or these two mentioned. There is info in the stickys in the New Collector sub forum that will give you an idea of the pictures needed to evaluate the pistol.
http://forum.lugerforum.com/showthread.php?t=31977
Better pictures are needed to get a "value". I collect police lugers and may be interested in it, so will not "price" is and leave that to someone else.
Price/value on lugers is highly variable depending on condition of the luger, and where/how/when you sell it and of course how "popular" the specific variation is.