Whats it worth.....

My dad has a Walther P38 9mm that I longtime friend gave him several years ago. He is not looking to sell it but we were curious to find out what it might be worth, it is blued. I may be asking questions that I shouldn't be since I wasn't able to find a website that would give out free estimate value quotes. Probably a lot of other variables that would need to be known about the gun to accurately price it also.