Mike…

The word “mint” is, indeed, a coinage term. However, at dictionary.com, there are a total of 12 definitions of the word “mint” listed, most of which have nothing to do with coinage. The word “mint”, and more specifically the phrase “mint condition” as relates to chips, automobiles, beanie babies, etc.. is covered by this definition:

adj : as if new; "in mint condition"

That said, you are absolutely correct in stating that this perfectly valid description of a chip is very often misused and abused by unscrupulous or ignorant eBay sellers. As far as the official chosen (and, in my opinion, unfortunate) description “new” is concerned, well, I’m afraid that we have to live with that. To me (and many others), the connotation of “new” as relates to a chip indicates that it has just been released. If you ever see me auctioning an older obsolete chip in perfect condition, you won’t find word “new” in my auction. It's OLD, dammit!