Is this an original or a reproduction? It has FOMOCO in script on each blade but no other markings.
I would say a repop. No date code or balancing weight.
Unusual for a old repro part to have a Fomoco trademark given civil liabilities. Blades are not shaped like is typical. Maybe very old. Not original for any 65/66 hipo Mustang at the very least regardless of date code or balancing weights.