Sounds like you may have a Ted Williams 300, made by Winchester; same as a Winchester 1400.
To set the choke correctly, screw it all the way down. It should stop just beyond Full; then back it off to what setting you want. You should feel clicks. It doesn't have all the settings printed on it. The click between IC and MOd would be Skeet 2; The click inbetween Mod and Full would be Improved Modified. It can be also unscrewed all the way off for cleaning.
Good guns. I had a TW 200 (Winchester 1200) the pump version. I shot that gun really well. Grandson inlaw has it now.