They did use mahogany as the outer ply on the wrapped drums (as did Ludwig all through the 3 ply era, even on most of the later wrapped clear interior "maple" drums). The M denoted either a maple finished shell to be stained/painted or a higher quality mahogany outer ply to be finished as "natural mahogany". The others received the P stamp, "P" for pearl but it meant a shell that was destined for any wrap. I have little doubt that there were exceptions where drums with maple (or nicer mahogany) outer plies did get wrapped, but the intent of the stamps was to differentiate between drum shells intended to be wrapped and those intended for paint or stain/lacquer.I thought for the most part mahogany was the wood used under the wrap to save on money. Why use a select maple wood on the outermost ply only to wrap over it? Did they have so much maple laying around that it really had no difference in the cost? And wouldn't the more porous and softer mahogany take the glue better to give a more secure wrap?