DWM 1908 military luger

It is dated 1910 on the chamber, four digit serial#, with imperial marks on the grip frame that connect it to the 6th Division, unmarked mag with wood bottom and the grips are clean and sharp. The bad thing is that the bluing was stripped many years ago and buffed with 0000 steelwool, just a trace around the toggle. Mechanically sound and appears to be all original, the Blue Book only goes down to 60% for $700 . I need an idea of where this should fall for value , books are a guideline for value but where do functional lugers like this fall for value??? So much info out there it gets confusing, was looking to use it in a partial trade for a Garand with another gun but not if I dont have to.