New old stock (abbreviated NOS) refers to obsolete equipment, or original parts for obsolete equipment, that have never been sold at retail.
The term refers to merchandise being offered for sale which was manufactured long ago but that has never been used.
Such merchandise may not be produced anymore, and the new old stock may represent the only current market source of a particular item.
Although not an officially recognized accounting term, it is in common use in the auction and retail industries. For example, owners of antique vehicles seek NOS parts from specialized vendors that are needed to keep their automobiles, motorcycles, or trucks operational or in factory-original condition. eBay uses the term on their auction web site.
While damage to the original packaging is common, damage to its contents is generally not acceptable in determining if an item is NOS, as it should be presentable in the same form as when new.
Some people refer to such merchandise as new obsolete stock to further indicate that the parts have not been manufactured for several years. This describes parts that are used in obsolete equipment or the like.
Other people refer to new original stock meaning that they are original equipment parts that remained in inventory for a use that never came. Other specialty parts vendors then market these NOS parts that may either decline or increase in value depending on their type and desirability.