“Marks on the underside”


I sold a piece of equipment on eBay and described it as having only slight almost invisible blemishes.
The buyer requested to return it to me because of “marks on the underside.”
I granted the return without delay.
Now I’m having second thoughts.  My question is, do marks on the underside which obviously are not visible when in normal use, count as a valid reason for return?

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Surprised he returned it (he had to pay for that, right?).   I've had buyers (and I'm sure others here have as well) who will agree to a price, then will use the "there-are-scratches" routine to get you to lower price at last minute.  All you have to do is say "No thanks.  I'm not worried about selling it."  But if I read an ad like that and wanted to buy it in good faith, I would DEFINITELY ask first for a description or picture of those blemishes.
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Not sure I’ve ever even looked at the bottom of a piece of gear... seriously, who does that? I’m with the rest. Not worth the hassle. Buyer pays return shipping, get it back, refund. Be done with it. 
Overstate blemishes and detail them in photos. Let the buyer decide and cover yourself.
Always include Hi Rez pics of every surface (underside incl) & describe every mark accurately.