[Mr70]

I'd say that's an original #6412293 7K Tach you have there for a 1965 Passenger 4-SPD. w/T. Ign.w/H/Per.or Sp. H/Per 396 or 409.
I believe Delco-Remy manufactured these gauges originally?
Delco Remy did number some of their own parts differently.
They weren't always as the Chevrolet parts pages declared.
Example:
I have a set of NOS 1st design 1970 Chevelle Tail lamp lenses.The Chevrolet parts books say they used part #5963045-LH & 46-RH.The Original boxes show these same numbers stamped on them as well.
When you pull the actual tail lamp lenses out of their original boxes,they have #5963047-LH & 48 on them instead.These two numbers do not appear anywhere in Chevrolet parts literature,yet they do exist and are the proper parts for the 1970 Chevelle application.
This and yours are just some scarce examples of Delco parts numbering anomalys I have seen and heard.