I'll have to dig into my old Herter's catalog to see just what model is what. Last weekend I saved two in 12ga. from become fish structure (literally!) for $10 each and a small box of parts. Almost got a hernia carrying it all to the car. I figure they should last about as long as the Japan nuke power plant waste.
Now to figure out what does what; wish one would have been 20ga.
Update: yep, they are 72's and there is a decent description of use in the catalog, #84 of 1974
New, c/w ga. set and powder/shot hoppers was$59.97, conversion gauge units were $9.97; Ive no idea what the string would do. except maybe hold the handle up when not in use.