Is it possible that the gun is, in fact, 'mobile' choked with a friction drive system that uses no notches?
If so, you should be able to detect that by looking at the muzzle rims. I've seen that job done so well that you have look pretty closely.
As far as what 'we' think of the chokes, what matters is what 'you' think. And you can shoot any 2 3/4" shell you're comfortable shooting in that gun.
It likely has an inertia set second trigger, although that's not a 'for sure' until you try it. If so, it will require at least a snappy one ounce load to set the second trigger.
The bore size is standard Invector +, and the gun almost certainly has long forcing cones. It's intended for modern plastic wad ammunition.