The special order paint Shelby's are different from the special order paint Mustangs and Mach's that the Shelby was based on. Since the mirrors were painted by the suppliers the Mustang's order with special paint didn't have painted mirrors but they were substituted with a single drivers side chrome remote mirror. This suggest that IMHO the mirrors were painted at AO Smith for the Shelby's
Of course it's always risky IMHO to use promotional, advertisements or prototype pictures as a single source for facts.
Don't know that I've ever disassembled a special order paint 69-70 Shelby. Anyone for overspray on the control mechanism, cables and or back side of the mirror to support this possibility?