The copper sulfate sure brought out the twist. Never heard of Remington doing what Greener called "sham Dam," I am confident that is the real thing.
The dealer was at best ignorant and at worst lied.
Remington made good Damascus but it was still Damascus and is over a century old.
I would think twice... and hang it on the wall just like the one on my neighbor's wall. Except his already has a chunk blown out of the left barrel. He was a gunsmith and kept it as an example to people who wanted these relics fixed up to shoot.