The Magnum-Ten NID takes an idea from the Model 21 in its much longer frame then the standard NID. The magnum frame NID also has a larger diameter hinge pin and the lug extension through the bottom of the frame. It has always been interesting that the Olins went to Ithaca to build a gun for their 3 1/2 inch ten gauge shell. I wonder when that request was actually made and the plan hatched. The Magnum-Ten first appears in the 1932 Ithaca catalogue. Was the plan made with Ithaca before the Olins bought the defunct Winchester Repeating Arms Co.? Why didn't they just build a Magnum-Ten Model 21?? Western Cartridge Co. did have a track record of working with double gun manufacturers with the original developement of the Super-X and the Super-Fox gun to handle those shells a decade earlier.