You're correct- some red hazard switches had lettering and some did not. The lenses all unscrew and can be swapped, as can the knurled retaining rings. Matter of fact, entire switches can be swapped but the switch wiring letter-codes embossed on the back varies. A few minutes work with a VOM can sort them out. That includes ones from FIAT, Alfa Romeo and other '70s Euro cars. I've seen both series of switches and both lettered and plain lenses on various years of Panteras. Many vendors carry new switches.