Remington still offers a weak, watered down 200gr FMJ in a nickel plated case in 10mm. Or, they have within the past year anyway.
This R10MM4 -- was the slug just a "typical for the era" copper jacketed JHP?
I'm not trying to make an argument, I've just always been fascinated with the history of 10mm ammunition. FWIW, the Silvertip is a "decent" round, but know going in that you have a very old-tech bullet and the velocity is certainly not top-drawer for 10mm. From my Glock 29 (2.78" barrel) they chrono at 1,106 FPS average.
Another blimp on the radar: as far as I know, and unless someone can offer contrary information-- if you find a nickel plated Winchester 10mm brass, it most likely came from Black Talon 10mm ammo. I don't believe they sold it any other way, but I'm unsure if they sold it in component form.