Check the locking bolt for a serial number. Which side of the bolt is it on? Left or right? Now the condition of your Luger is very poor and at 50% the book value is about $1000. I don't know if yours even rates that high. But it is a good find and depends on how much you paid for it. Now they made 12000 1900 American Eagles and only a few were US test models. But if yours is then you can add about 40% to the value of it.