It's my Uberti 1858 Remington with a .45 Colt cartridge fluted conversion cylinder.
Next two below pics after restoration.
It's not nickel nor stainless, but carbon steel and it's "in the white" (bare metal finish), after filing pits, sanding and I highly buffed/polished it (and keep it waxed) to restore it from the way it was pitted and abused with some kind of acid etching before I got it (next two pics below).
Worst pitting was on left forward top strap (filed and sanded it all out). Most of the rest was not deep acid etching most likely by "Bubba" to remove original bluing. Had to use a sanding block and be very careful when buffing to not round out the flats on the barrel.
After filing pits out, sanding overall to remove acid etching and first initial buffing (lots more buffing afterwards to make it look like it does today in first two above photos).
Hi:
Your Remington Model 1858 appears to be cut down from the original model grip and barrel ?