I inherited 2 Mossberg 12g 28" 2.5&3" modified choke barrels. The barrels do not have the top ribs, just the brass bead.

No idea if these have any value. They look to be in decent shape.

Anyone have any idea what they should be listed for?

Following for curiosity

Assuming they are for the 500 and not some other, less popular model, I'd guess about $50. Those are not 'high demand' items.

That is my estimate as well (although to be fair, I wouldn't give you $50 for one of them). These were the really low-end barrels (no vent rib, fixed choke) and were the cheapest barrel Mossberg offered. And also common as dirt, and the barrel that a lot of people replaced with something better.

Read what is says stamped on the barrel. If they are not good for steel shot those are the barrels that get cut off and mated to an adjustable choke. Now if they are for model 200 pumps they might be worth a bit more money. We really do not know what you have.

Thank you for your input so far guys. Here's a few pictures. Looks like the are not quite as I remembered. One does have a little corrosion where the nut is, inside the barrel is clear.