I used to sell them, if that helps. "Reinforced plastic" basically meant a polyester resin composite, most likely fiberglass, though somewhere I have also heard nylon cloth mentioned. The boatbuilding nylon that I have seen though (as in Phoenix kayaks) was quite prone to delamination and nowhere near as clear as the cloth on a trapper. The Trappers generally sold to rich people, as they cost two or three times the price of most canoes, and an amazing number of those we sold were impulse buys. People really like the wood showing on the outside.
I don't know if they ever shifted to epoxy resin or not (they should have as it became available, because it works and lasts without delamination a lot better). As for durability, I can't say much. The people who bought ours generally were not the type to take it out and grind it down a rocky river or leave it outside in the back yard on saw horses. Those canoes had a pretty pampered life.