When describing 356 car parts, a variety of acronyms are tossed around, frequently without defining them, resulting in a great deal of confusion for newcomers and old-timers alike. This is an attempt to clarify the generally accepted meanings of "OEM", "NOS", "NIB".
OEM: "Original Equipment Manufacture", sometimes shortened to "OE". Most members of the 356 enthusiast community would agree that "original" implies the part in question was manufactured and intended for use in a specific 356 model, by Porsche or one of their licensees. Sometimes the part was only used by Porsche, though sometimes it was also used by other auto manufacturers (for example, the K2665 and K12627 front turn signal units used on the 356B and C were also used by Mercedes on the 190SL). OEM parts would include inventory overages as well as identical specification inventory manufactured to be use on subsequently produced automobiles and to provide replacements during the initial inventory supply cycle.
However, after those inventories were depleted, an original manufacturer or an original licensee or a new licensee would build parts for OEM inventory that may or may not be identical to the initial run, yet functionally and cosmetically indistinguishable, and that is the point at which the term "original" becomes muddled.
Additional confusion occurs because often parts were made for use as replacements after the production of a 356 model ended, but were made to different specifications! An example is the A/B fuel tank cap. Porsche sold replacements for that cap long after 356 production ended and the replacement part looked quite different from the version that new 356A and B owners received with their "right off the showroom floor" cars. But to Porsche, the cap was the same part with the same part number.
In any case, it seems reasonable to say that the later part is not "original" since it was not produced during the time the car was being produced, nor was it manufactured to the "original" specifications for that part. It could be from the OEM, but not as originally delivered, and by definition would be a post-production part. In other words, it represents inventory manufactured after the "original" part inventory was depleted. This is a key distinction between original and everything else, as that part was not available during the initial manufacturing phase. So how could it be "original"? It was not the same nor was it made during the initial phase of manufacturing of the vehicle for which it was intended.
NOS: "New Old Stock" is generally accepted to mean parts produced during the initial production run (when the 356 was a "new" car, from 1949 to 1965) and that have never been used on a car, therefore they appear "new", or at least as new as a 50-year old part can look. They would certainly be "original" as well. This term can be used incorrectly when applied to new looking parts that were actually made after the 356 was out of production, but some would argue that any replacement 356 part sold by Porsche in unused condition can be called "NOS".
Regardless, parts made during or after 356 production by companies other than Porsche or one of their licensees, even if they could be used as replacement parts on a 356 but were not used by Porsche when the cars were new are not "original" nor are they OEM.
NIB: "New in Box" is a term that has very little value, but we include it here because sometimes it is used by part sellers (often those on ebay) as a way to try to add value to a part. It can only mean exactly what it says: that the part is unused and in the box provided by the manufacturer. It does not mean the part is OEM or NOS.
To sum up: