What is the value of a nickel-plated bone handled German luger officer's gun?

You probably have what is commonly refered to as a "re-nickel" pistol. This means that the nickel is not the original finish. Also, the grips as described are not original either. What you have is a "shooter" not a "collector" pistol. This being said, and without actually seing it, it is probably worth $200-$250 depending on condition.