A few years ago I was feeling frugal and bought some .325 Narrow Kerf chains off eBay. Some were 'used once, never sharpened'; some were 'new old stock' (NOS). They were a good deal, at about $6 to $7 per loop, including shipping. I guess that these do not sell as well as other sizes, as both sellers contacted me, asking if I wanted more.
I took one of the NOS chains, still in the box, to a GTG, where I was going to compare it with a new Oregon NK chain, and a used, but sharpened Carlton one for reference. I was slightly embarassed that I mounted it on my saw backwards, but everybody has done that. So I took it off and mounted it the 'other way', only to find out that it was still wrong. It was exactly like the one shown, with about 4 or 6 cutters backwards.
Apparently, somebody had tried to use up a short piece of chain, or make a larger loop, made a mistake, and placed it on a shelf. It stayed there until this eBay seller bought out the shop inventory when it closed. I don't think that he knew either - probably did not look that close.
Easy fix when I got home, but a surprise in the field.
Philbert