I imagine BM & BMM are the same, just a different way of addressing the colour. Same with Firemist Gold/Firemist Gold Metallic. In your pics you can see the metallic grains.
I know people do that, but I think that's an example of the cold/hot technique to artificially create chequing. To imitate the delicate flow and variety of the lines, making them look natural would be difficult beyond most finishers capacity. It would need to be performed with the skill, eye and deftness of an artist. I'll be impressed to be fooled by chequing done with a razor that looks that natural up-close. If I were to do that - it would take many hrs of much concentration and study of the way chequing flows - not to mention overall composition and balance of the lines. I've studied the way glasswork shatters and have always loved the aging effects like chequing and discoloration. Most 'relic'ing' is fairly pedesrian up close. The high end would be like a skilled counterfeiter - magnifying glass inspection quality.