Unless that guy had hands the size of Wilt Chamberlin that was not a 45/70 Remington Keene. They showed him loading it, that cartridge was no bigger than a a .45 Long Colt compared to his hand. Even though they tarted it up with a scope, it looks like a repro of the small frame Keene that the Interior Department bought for the Indian Police departments.
There was a big frame Keene that was .45/70 though, went to the Army trials in 1879 opposite the Winchester/Hotchkiss, Sharps version of the Swiss Vetereli, and the Remington/Lee. But Remington produced only a few hundred of them. Due to the Interior Dept. contract several thousand of the small frame 44-40's were built.
It looked to good to be anything but a repro- but I have no idea where they would of got one, havent seen any offered for sale.
Then again that 1876 Winchester carbine was also too good looking to be an original. Haven't seen a repro of it in the magazines for sale yet either.