Is it 2 or 3 pin?
Did you count the pin in the grip?
I own both and don't find one any better than the other.
Pics found on the net..
Does the grip have finger grooves?
If so, it is a Gen 3 or even a Gen 4, if not, a Gen 1 or 2.
I prefer a Gen 1 or Gen 2 over a Gen3 or Gen 4.
I don't care for the finger grooves.
Here are the different generations.
Also a G17 should have 17 round mags, a G19 has 15 round mags..
Regardless of the answers to these questions, if the gun is in great condition, I feel $400 is a fair price..