I brought them as part of a 89 Fisher Procaliber second hand off someone I trust (but not on this forum). There are a few little chips here and there, but these look more than coincidental. I did hold the rims up to a powerful light when checking over to see if the crack had gone through.
That said, these were quite dirty with brake grot, I took the pics as soon as I noticed the issue.
I'm going to go out to the Garage to take something done anyways so I'll have another look.
They're Araya, can't see a model number but states the size (26 × 1.5) and they're on Deore hubs.