First off, thanks for this site. I inherited an O/U from my grandfather and should have done all this while he was alive. Anyway, there are chokes that screw in to the barrell of the gun, they just screw in finger tight, no key . They are not stock. They are silver in color and they have no markings except Mod and L. Mod. My grandfather shot skeet religiously. I know this is not much to go on, but can someone:A) Identify these chokesB) 'School' me a little on Mod and L. Modthanks all,Hank.