Cobra Tach

[NGT350]

I have seen a Cobra Tach for sale that I am puzzled by.
Seller claims it is for a 6 cylinder, is date coded Nov 1965, and is a rare original item. It has a chrome cup and dash mount, but the puzzling thing is, it only has a scale to 6000RPM.

Any idea if this was a thing? An over the counter accessory item? Or is it a fake?

[69mach351w]

OTC

[TA Coupe]

I would not expect most 6 cylinders to be going over 6000 back in the day.

      Roy