BillCA:
I looked at the M63-0 this time, and the serial number(Strangely)doesn't have any letter prefix at all? After opening the cylinder, stamped on the yoke is just s/n 72462(EXCEPT, just below this s/n is an "Upside down" B1(Whatever this means?)directly in the center of the s/n(Just below it!)?
Whenever I had first, reported the s/n as #72462, I took this s/n directly from the Sales Receipt-and, I had just "Assumed" that the letter "M" should have been typed on this receipt? What do you make of this s/n now? After opening the cylinder, the model 63 is stamped on the frame as Mod. 63!