I only buy parts from Mouser and Digi-Key and have observed for the past few years all Texas Instruments PDIP parts (e.g. 74HCT series) have sort of a dull finish on the pins. If I scratch it with metal it's shiny underneath, so I guess it's some kind of oxide layer.
The parts I buy all work fine though I use dual wipe sockets and don't solder them to the board. I've dug out some old projects from years back and the oxidation (if that's what it is) looks no different than how it looks on the new parts. So whatever it is, it isn't getting worse with time. The old projects still work fine too.
In comparison PDIP packages from any other vendor (NXP, OnSemi, etc.) purchased from Mouser/Digi-Key don't look like this. It's only Texas Instruments.
I'm tempted to say it's not a big deal, but I still don't know what I'm dealing with. Any ideas? Do they just use a different metal for the pins compared to other manufacturers?