The Ancient Pseudoscience Station cannot drop Chess Trinkets even when they're unlocked.

When hammered, an Ancient Pseudoscience Station has a chance of spawning a handful of any of the numbered trinkets. However, this will never spawn the Chess Trinkets (white/black bishops, rooks, and knights) even if they have already been unlocked. This seems unintentional, as spawning an APSS on the surface and hammering it WILL spawn Chess Trinkets, but it will never happen in the caves where the APSS is actually found.