A second look.....
A second look at the copper rivets, and the metal rod in the dadoed underdeck shows that the rod has nuts on each end, and probably emulates the Thompson metal strap. I'm assuming that it held the inwales together while on the form. That still leaves the copper nails, or rivets and their removal. Could they be big ring nails??
Andre, the punch and drill sounds like a good avenue.
I'm kinda waiting for Dave Wermuth to chime in. According to an old post of his, he was less than happy about the darned things. I wonder why screws weren't used as in the rest of the fastenings..
Also, it seems as though Shell Lake canoes rank among the lowly bottom feeders in the world of wood/canvas canoes. I'm not sure how I developed that opinion, but this canoe appears to have been very well built. The red cedar planking is tight and quarter sawn. All trimmed in mahogany, except for white oak stems and oak seat planks.
Dave