I can add a few details.
The front cylinder edge of Mountain Guns are beveled. That's called a black powder bevel. The only sight combination I've noticed on Mountain Guns other than a plain black ramp front and plain black adjustable rear is the red ramp and white outline on the .45 ACPs made about 2000.

.41 magnum and .45 Colt Mountain Guns were made in blued and stainless, one batch of each color in .41 mag., one batch of blued .45 Colts and multiple batches of stainless .45 Colts.

I don't think Mountain Guns were ever continuously available cataloged items. They only came out in batches, apparently when distributors ordered them. Some of the batches like the .41s, blued .45 colts and .45 ACPs were never repeated so they only exist in small numbers. The only cartridge that was repeated often enough that you've just about always been able to find one is .44 magnum.

When they were introduced they were the lightest big bores S&W had produced since the .44 specials made in the 1980s and the lightest .44 magnums made. They lost that claim to fame when the aluminum & titanium revolvers were introduced in the 1990s.

Edit to add: colt saa got part of this up ahead of me. That happens to us slow writers. He also posted a picture of one I forgot, a blued .44 magnum commemorative. Since were adding commemoratives, there was also the 1994 Springfield Armory Commemorative .45 ACP which was a Mountain Gun in every detail except its name.