WHAT DOES RM66 MEAN?

Is also the revolver 6 inch design drilled and tapped below rear sight to be used which has a pink dot mount adapter It seems like it’s about similar to the S&W 357 magnum revolvers with adjustable rear sightsThe suggestion in the crown receives concluded with a little cranium insignia to be a refined nod into the RM 052 Tourbillon Cranium check