I've had my 12 gauge 30 inch barrel, 3" chamber, fixed choke which I believe to be modified and full, I can check this later and send photos if it will help.
It's a 1981 Citori over and under and decided to sell it to one of my friends that's wanted it for a while. it's in pretty good condition with some mild wear for being a 40-year-old gun there is some small pitting in the top barrel about a quarter of the way down on the inside. Trying to come up with a fair value for him, I do see $800 to $900 it seems like on this gun but I can tell it varies based on chokes and condition.