Garnett,
A couple points.
1. Savage has always been kind of a half-witted company. I honestly think they made some of the best, most useful guns...purely by accident...or through acquisition of Stevens, which was a very innovative company. Case in point is the Model 42, which was a re-introduced and "modernized" idea after the Model 24. But they so utterly botched the job, that people on the Savage 24 forum regularly laugh whenever someone brings up the new 42. It's $350 plastic junk. And there's a HUGE following for model 24s, so if they had put the time in and come out with an $800 gun with great caliber choices, they would have sold like hot cakes. But they literally don't understand the appeal of the very gun they sold so many of. My point in saying all of this, is that Savage is of very little help these days. They make very accurate guns, but they just don't "get" a few things. I love my old Savages, but sadly, that doesn't make the company lovable.
2. You will often not find USPTO numbers associated with a model name. So I would suggest searching under "single shot rifle" patents, with variations naming Savage Arms or Stevens Arms. My hope is that Frank DeHaas already did this work decades ago, but I don't have a book on hand. He definitely dedicated an entire chapter to the model 219. He is and was an authority on American made single shot guns. His daughter-in-law very kindly printed and mailed me that chapter a while back, as the book is long out of print. I'll scrounge and see if I can find it, and if so, will note whether he referenced any patents.
Old Frank had to do his research the hard way...the card catalog and lots of paper at the library!
Chris