The gold flash finish on the mating end provides corrosion protection for occasional disconnect cycles; for applications requiring frequent mating, the thicker 30.0µin (0.76µm) gold on the 5066682-9 sibling is the better call.
Gold Flash vs. Thicker Gold — What the Plating Grade Means
The 5066682-6 carries a flash gold finish, which is a thin layer applied primarily to prevent oxidation during storage and initial assembly. It handles a few dozen mating cycles reliably. Compare that to the 5066682-9, which has 30.0µin (0.76µm) of gold — that's a measurable plating thickness that supports hundreds of mate-unmate cycles in field-service or test-point applications. If your BOM calls for the 5066682-9 and you're considering this as a drop-in, the plating difference is the deciding factor: flash gold is fine for a one-time install, not for repeated reconnection.