I purchased a Mossberg anniversary gun from a shooter roughly 20 years ago for $200.00. That was the only one I ever saw. He said it was made in 1967 or 1968? It was on the 500 frame and it had a beautiful a Monte Carlo trap stock and forend along with a 30 inch full choke barrel. This gun I gave to my son in law.
The AHT is an interesting trap gun. Simmons put them together with Mossberg parts. They are basically a Mossberg 500 with a Simmons Olympic Rib, High Comb butt stock and a back bored barrel with Invector choke tubes. The .735" bore is what makes these guns kind of special. They are FLAT shooting guns that pattern and perform well with an aftermarket extended MOD choke tube. They are a lot like shooting Remington 870 TC with a high rib barrel.
$400 to $450 is about right for an original in nice shape.