Never.
As an owner of a
PCA secondary set as well as both leaded and unleaded sets my opinion is that it makes a difference and there's zero chance I'd want to use an unleaded chip to slot into the
PCA set. But that's just me.
Depending on the chip you select and particularly if it's a 43mm chip, maybe you don't notice that much - but it would personally tilt me just knowing.
For me, I'd much rather use a plaque here, there are a few good
PCA-specific options that aren't impossible to obtain, won't require murdering chips and you don't need to worry about spot progression and/or color. That's the route I went, albeit I was lucky enough to get my hands on these Matsui plaques.
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There was a group buy for some
MSK plaques and this member may have some available still:
https://www.pokerchipforum.com/thre...he-admiral-pca-msk-plaque-sample-sets.100302/.
There was also a Cards Mold GB and I do own the $50s from that one and they are pretty great.https://www.pokerchipforum.com/threads/
pca-plaques-cards-mold-gb-order-thread-closed.79763/
I'm sure with some effort you could track down some of the $1ks.