Acronyms are nice for writing but terrible for new readers.

The two "MRDs" I've worked with are the JSB 13.43 Monster Redesign (.177 caliber) and JSB 25.39 Monster Redesign (.22 caliber). They both exist in addition to the original Monster that has a fuller, straighter waist section and short, distinct skirt. And in the .22 case, there are now three variants as JSB changed the skirt pocket shape and for a while you had no idea which style would be in your next tin.