I have a number of foreign chips, most one of a kind.

They don't attract much attention, so you can find bargains. There is no guide, and it's hard to tell if someone bought 5,000 chips, or pocketed two, on vacation. The obsoletes, may be rare or common, without any way for any of us to know or assign a value.

Armin Pfaender had quite a batch of foreign chips a while back.