Technically, NOS means New Old Stock or New Original Stock. It is sometimes misunderstood and misused. If it really is NOS, that means that an original Mopar (or Ford, GM, etc.) part sat on the shelf at a dealer or parts distribution wharehouse somewhere for 30 years or so. Maybe it got lost in the shuffle and found later? Who knows. Anyway, somehow that part winds up for sale 40 or 50 years later. NOS parts may, or may not be good.
May be good: If it REALLY is an original part (preferably still in the original box) that just never sold, it is probably a wonderful thing. However, as mentioned below, there can be problems.
May not be good:
It is entirely possible that the reason a part sat on a shelf at the dealership for YEARS is that it was defective and was not thrown out. Let's say that in 1972, a Plymouth dealer body shop ordered a 71 Cuda fender, and it fit poorly. They would order and receive a new one but what happened to the defective one? It is entirely possible that it found its way to a swap meet 45 years later as a rare (and expensive) NOS fender that may not fit so well. I have also heard (not substantiated) that when a part didn't fit quite right on the assembly line it would be set aside and placed in the parts inventory waiting for a dealership or body shop to order it. Maybe they figured that professional body men would not mind tweaking a fender to get it to fit??? Another thing to think about is buying an NOS electric part. They have been sitting for 40-50 years, and that might not be too good for electric circuits and contacts. I bought an NOS gas gauge about 20 years ago. It looked great, but it did not work. And yes, I did diagnose that the gauge was definitely the problem. I wound up mailing it in to a specialist to be repaired. Then it worked great. He said he saw a lot of that with NOS gauges and other electric/electronic items. So I paid for that part twice. I AM NOT SAYING DO NOT BUY NOS PARTS, but I would buy them from someone I trusted. That way if it did not work/fit, a refund/adjustment is possible. Also, some sellers will consider a slightly used 45 year old part to be NOS. If it is original and in GREAT condition, that's great, but to me it isn't NOS.
