Sorry to hear of your troubles with Gunbroker, but, not surprised. Reason being is I saw what they call a No.4 Mk.1/3, meaning it was a Mk.1 upgraded in the 1950's according to the listing, and bidding in the $400 range.
I had my fun with these when they were cheap, and surplus ammo was in good supply. There was this "Dime Store" in Fayetteville NC and can't remember the name, but, they sold surplus rifles, and one of these could be bought for $69, they'd put 3 greasy boxes up on the counter and I could pick thru them, and found one that looked refurbished or new! They also had Mosins for $49. I Lost interest at some point and sold them, really wish I hadn't, but them's the breaks.
Last attempt to pick one of these up it was a brand spanking new No.4 Mk.2, one of the contract rifles built for Ireland in 1955 I think, complete with a bayonet #'d to the rifle, but, because of the strife going on they were warehoused and never delivered is the story, and $700 was the price...