I have two 39s. I agree. But the only info I could find on a G is that it was a pump gun.
How old is it? Is this a collectible of some sort that isn't obvious?
One of my 39s is a rare variant (tapered octagon Mountie that looks like a Marlin "Cowboy" series gun), and in ~98% condition. I paid $400 for it at a store. My 39A was around $500 new, a couple years ago. I think the price of that gun is too high, unless there's a peripheral reason for it (rare barrel length, rare combo of PG and barrel length, etc.).
What's the "g" in your question, then?