Wow John thanks, that is strange. Looking at the pics I see some major differences and actually considerably harder to make then the one Tom Burgess made. (the added difficulty would be in the area of cutting the hinge shape for the blade to rotate on. Perfect work for a wire cutter or a shape end mill) It may use the over the center pin concept which would not surprise me as being harder to operate. However, being stiff has it's advantages over the issue Fred was concerned about. Wish you could have gotten a pic from the top but I certainly do appreciate the 2 you posted. By chance you didn't get the name or info of the rifles current owner?
I guess I should have taken a picture of the right side. The right side of the hinge pin on the one at the show had a large diameter head, just like the right side of the one you originally posted. It also did not rotate with the blade but stayed stationary relative to the base. I wonder if the small end of the pin might not just be a press fit in the left side of the base. The owner was not there either time I stopped by, but his friend behind the table did say that the metal work on this rifle was by Burgess. The rifle looked to have been more recently stocked and reblued. I am sorry but I did not get the name of the owner.
John