New old stock

New old stock (NOS), or old stock for short, refers to aged stock of merchandise that was never sold to a customer, but still new in original packaging. Such merchandise may not be manufactured anymore, and the new old stock may represent the only current 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 classic, vintage, and antique vehicles seek NOS parts that are needed to keep their bicycles, automobiles, motorcycles, or trucks operational, or in factory-original condition. These owners put a premium on NOS parts. 
Another example is businesses catering to vacuum tube enthusiasts that define NOS as any stocked item which has been sitting on a stockroom or warehouse shelf for some time, in addition to stocked items which are no longer being manufactured.
Another definition of NOS is new original stock, meaning that they are original equipment parts that remained in inventory for a use that never came. Automobile dealers and parts companies often sell such slow-moving stock at a discount. Other specialty parts vendors then market these NOS parts that may either decline or increase in value depending on their type and desirability.