Help! Epoxy-like substance on wheel?

[o2bndair]

I am looking at a 2007 XLR. There is a light gray material splattered in the cutout areas of the left front wheel that looks like an epoxy material. The seller is willing to replace or clean the wheel but I am concerned about where it might have come from. Any ideas?

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[monepit]

I've had the same on mine before. Don't know where it comes from. It's never caused any problem though.