I bought an ASM 1851 .36 that was only marked with a faint ASM under the loading lever. There were no Italian proofmarks or any lettering anywhere, not even the Colt address on the barrel top. I don't think it was defarbed. I've heard some bad reports about ASM but this little 1851 is smooth and tight and pretty - a great shooter.
But there is no-way, no-how you will ever find an original 1800s percussion revolver in that condition
I suggest you check out the James Julia auction in Maine this fall. They sell many pristine, untouched, perfect originals. Very pricey but they exist.