Researcher most likely has this info on the tip of his fingers, but best I recall Ithaca made 877(?) magnum NID's with 87(?) in 12 ga. with the balance in 3.5" 10 gauges. My magnum 10 was made in 1938. In an earlier thread there was commentary that some of the 12 ga.guns now have ringed" chokes from large shot bridging at the chokes.
Gil