As far as I know, the P or T stamp on the forend hanger is indeed the most reliable indicator of Ithaca assembly... aside from the guns that actually have Lefever Arms Co., Ithaca, N.Y. stamped on the sideplates.
I have always felt that far too many guns with unusual features are wrongly attributed to Ithaca assembly. It never made any sense to me that a Company with chronic financial difficulties would have frames and components for many thousands of guns in inventory at the time of the sale to Ithaca. If you study them long enough and look at all of the apparent out of sequence serial numbers, it seems to make more sense that quite a few guns that were prototype models, or perhaps contained experimental features, and were probably evaluated, tested, or otherwise held back before finally being sold to either the general public or employees. Dan Lefever and his sons were always tinkering with the design. Some features were very short-lived, which can make it difficult to find parts at times.
