The lens cannot be removed without disassembling the unit.
The black plastic sliding piece also cannot be removed without disassembling the unit.
The unit is bradded together, and the only was to disassemble it would be to grind the brads off, which would require replacing them with screws or something for reassembly. This unit has not been tampered with like that.
The black sliding piece has a round hole indicating this is correct for the 1970 style shifter. 71-73 cars have a rectangular hole for the T handle shifter. 74 cars have been reported with both the T handle & the 70 style round handle.
It might be possible that the factory installed some Shift Gate lenses into T handle shifter units, but I haven't seen any yet.
Dave Walden has told me that he tried to look into this when he was doing his Challenger, and couldn't find any pattern to the use of the shift gate lens. It doesn't seem to be related to build date.
If anyone has more info about the shift gate lenses, please post it. I'm all ears.
