The M prefix was intended to represent that it was a metallic texture.
The M Dwarven texture is a texture created from the vanilla dwemer metal ingot. As Albatross correctly guessed, this texture was used mainly as a colour reference when creating my M Bronze texture. The M Dwarven texture is lower quality than id like, it's also rough and pitted in appearance. M Bronze is a smoothly formed, higher quality texture showing tool marks. It is the M Bronze texture that is intended for use on completed items.
M Copper and M Corundum share the same relationship as M Bronze and M Dwarven, with M Copper being the worked and finished material of the M Corundum base.
The texture used in my final version glass weapons is the M Glass Malachite texture file applied diagonally at roughly 50% scale.
The Darker and lighter version of textures are meant to be used on accents of the objects to give for example, hilts and blades, distnct yet similar colours and textures.
Quicksilver weapons are M Silver for the texture and tool-marks with M Quicksilver for the unique luster.
My application technique was as Albatross correctly guessed. My first step would be to remove the saturation from the base texture. I would then use a Shadow/Mid-tone/Highlight adjustment to normalize those values to share similar shades of darkness with the Nordic Longsword texture, which I used primarily as a highlight/mid-tone/shadow reference, so that weapon style had as little impact on lightness/darkness as possible. I used Shadow/Mid-tone/Highlight adjustment instead of Brightness/Contrast so that I could manage the three values independently since some textures had brighter highlights than others, for example, and an across the board brightness increase would make the already bright highlight too white to accept an overlay. Overlays work more effectively with a grayer base than a whiter base. For gemstones and Ebony however, I did not use overlay. I used the application which is called 'Hard Light' to 'paint' the texture on the area. Hard Light is much harsher than Overlay and is not suitable for sure with most textures, though the more prominent Ebony and Gemstone textures do benefit form it's use.