John Russell was the son of W.R. Case. I wonder if this is the same Pneuman and he was perhaps once an employee of Case who went off on his own? The makings of a good story for the History Detectives series on PBS.
The patent is for an interesting looking ax and knife combo. I wonder if it was ever made? Steve?
The patent is for the Case brand Knife-Ax combo although the patent isn't related to the OP fixed blade. The patent date stamped on the Case brand knife-ax locking levers is Oct. 22 1935.
Case did manufacture very few fixed blades with the same type construction as the OP knife handle. Case fixed blade knives with this type of construction are extremely rare. I suspect that the relation between John Russell Case and Arthur H Pneuman had something to do with these early Case fixed blades.
The OP knife is very interesting especially considering this relationship.
If I have seen further it is by standing on the shoulders of giants.