see
http://www.bookfinder.com. they currently have three available starting at $175 (cheap) and up. I have seen this book going for as much as $425. It is one of the most complete and difinitive books written on the various proof marks and their location on the Luger that is available. I assure you that you will not be disappointed. In the search block enter sam costanzo then world of lugers proof marks. Another search with just the author name will bring up another one.