I've sold chips and the buyer has used the scans from the original auction and I have no problem with it.

In theory, your scan is your work. Forever. However since it's not an issue of someone who doesn't even have the chips, "borrowing" scans to sell some other chip or maybe scam the buyers, I'd say the chip and scan are partners.

Often the biggest issue is, whether the scan is the same chip as the auction. Since this isn't in question, no problem.