Miller,
I was hoping you would jump in. Do they have a picture of it? I wonder who was making it for them? 40-85, eh? It sounds very close to a 410 2" brass shell loading.
The Stevens 1909 catalog has shells for reloading. They list 38-35, 38-45, 44-50 and 44-65 for shot shell loading. These were supposed to be for their "New model pocket shotgun", though I have never seen any of the actual guns. I can only assume most were destroyed after the 1934 NFA. The few remaining Harrington Handy Guns need a tax stamp to be legal.

Pete