I have a rallye gauge cluster with the rare 5500 rpm red line 8k tach.

It came out of an even more rare 1970 Barracuda convertible with a 6 cyl.

I don't know if it was original. I don't know if it ever worked. I didn't care. I paid $80 for the whole cluster.

Hook both of yours up to the same car and see if the 5500 registers higher than the other at the same rpm.