There are four levels of quality in original parts. From best to worse, they are:
1. NOS (new old stock meaning a new part, never installed, still in the original packaging)
2. Nice originals (if you rated these items on a scale of 1 to 10, the appearance would be from a 7 to 9)
3. Core ( items with quality rating from 4 – 6)
4. Junk (items with quality rating less than 4 should be scrapped)
“NOS” is the most valuable of the quality levels. However, NOS does not always mean “perfect”. Poorly stored parts could have pitting, cracks, dents or other storage issues. Don’t assume NOS parts are perfect. Check them out first. Also, sometimes the new part was flawed and returned. I found a few NOS items in boxes that had “RETURN” scribbled on the box. Also, I’d like to point out that old time mechanics did not throw anything away. They often put the used part in the new box and stored it. Make sure your not buying the “old take off”. One last NOS trap to avoid is the decal kit from the old auto body shop. Back in the day, if your 1970 Super Bee got the fender banged up, the body shop had to buy the entire strip kit. They would use the decal for the one fender, then stored the rest of the kit. These kits are never complete.
This snippet of information is direct from Dave’s book “Classic American Car Parts” get more great part picking information like this and learn to run an eBay business selling classic car parts by buying the book today.