Interesting. I had always thought NORS wasn't necessarily a Ford part and NOS was a Ford replacement part. NOS wasn't necessarily assembly line correct, but bought from Ford back in "the day".
My frame of reference was the restoration of old cars prior to the mid 1970s and yes people had been "restoring cars" for several decades by then already, like restoring a 1903 car in 1912. Before the mid 1970s most old car enthusiasts NOS meant made during the production time frame by the original maker with the original tools. (Surprise, some companies make parts for production and some make parts purely for service in more than a few industries.) Ford made (had made) popular 1965 model year parts for more than 30 years with few exactly like production parts that I ever got into my hands. If enough people wanted 1966 Mustang front bench seats and hounded Ford to get some made they probably would. They offer in service what is 1) a legal obligation and 2) what is a ‘fast’, popular, and profitable seller.
Prior to the mid 1970s the business of supply parts to return cars to some resemblance of day one or even day two was very small. When I started reading Hemmings Motor News it wasn’t much bigger in rectangle or thicker in pages than a typical local swap and shop type magazine at your local convenience store. The largest section covered the 1928-31 Ford Model A car period and there were not many advertisers. Businesses like Kanter® were around and a few others that still exist. I don’t recall a single business that sold genuine O.E.M. factory parts from production or otherwise. The businesses were directed at keeping cars on the road and not maintaining them just like any factory created them. The quality of parts my father bought ranged from horrible to with enough effort you could make them work. I recall buying some brake parts for a 1930 Ford Model and not a single one of them would fit much less work. I took some parts to a machine shop to be fixed and had one made from scratch based on severely worn one.
These days there are sellers offering remanufactured parts as “NOS”, well it is from their frame of reference probably. There are also people collection dozens for very rare never installed assembly line versions of parts, using them to secure judging points, removing them after one show or maybe a whole show season, putting them back in the packages, and selling them as factory NOS. Once used they really are not “new” anything anymore, especially electrical parts that may have been damaged (cracked ignition distributor cap I saw offered for example).
The parts from any source, including the O.E.M., that were not exactly like the “originals” were some variation of replacement. Just because it comes in a Ford package doesn’t mean it is just like original.
Example: 1995 Ford F250 optional wheel center covers molded in plastic and chrome plated. They were fragile and easy to break. The first time from new truck my tires were rotated one was broken. The dealer service department ordered one. What came in was a redesigned stronger part. I tried to get another “original” but the service manager told me that Ford recalled all the “originals” and now the new one was all you can get. My truck was six months old and all we could get was a New Replacement, new meaning not the same as before.
Example: 2003 Focus SVT 5 Door center high brake light. During the first winter the red lens broke at a screw hole. The only thing Ford had was a revised design so that is what the dealer installed. The next winter it too broke. Again Ford replaced it and again a now third design was used and it could take going through cold weather. In that car’s case there was original and two different replacements UNDER THE SAME SALES NUMBER in less than two years.
Today it must be terribly confusing for car owners and restorers to wade through all the descriptions sellers use. I suspect is in part individual frames of reference. If for example somebody takes the effort, which can be enormous, to create a really authentic “replacement or reproduction” and it takes them ten years to sell all of them, then to him everything they didn’t sell immediately became their new old stock or new old replacement stock. Maybe somebody bought some of those parts but for any number of reasons didn’t use them, then them they might be new old stock. The situation I run into hunting Cobra parts are brand new replacement parts being sold in an estate sale situation. The wife, son, brother, et alii only know that part was purchased in the past and never used so top them it is new old stock even if it is a custom designed performance aftermarket part.
In summary, speaking solely for myself I do not rely on what sellers advertise parts as. It is up to me to identify what is for sale.
Dan