Tachometer lens retainer used on the inside of the cluster bezel to shield the face of the gauge. Will show a minor amount of wear or rust, plan on cleaning it up and possibly repainting. Almost the same as the speedometer lens retainer, tachometer version has a clipped section shaped like a thumb nail on the edge.
Stamped C7WF-10894-S or C8WF-10894-S. Also C7WY-10890
NOTE: The tachometer retainer is different from the speedometer retainer, the tach retainer is notched for the screw post in the bezel.