There are a few books out there. Can't recall titles to save my life. Go to the sports section of Boarders or Barnes and Nobile. They have books like that. Plus it's a bit funny to go to checkout at the registers with a book on guns or hunting and see the look on the face of the bleeding heart lberal working the counter
It still depends on condition, time of manufacture and markings. Get a copy of Fjestad's Blue book of gun values. Also reference Luger Tips by Michael Reese. Best way is to have an appraiser look at it.
Here is a very handy and effective device I use to dispense corn with - but it could also be used to dispense any other seed or deer feed.
I had an old feeder that had a failed motor... I made a set of brackets to attach the feeder to the rear of the 4 wheeler - the lower one encircles the feeder and has a forward section with holes drilled in the outer ends of the bracket... these holes align with two 5/16" bolts that drilled into the rack of the 4 wheeler.
The upper bracket is an "L" shaped...