Looking around Ebay, I came across this wall-wart.
Somebody actually thinks that "OEM" is a logical company name.
And If I'm not mistaken, it looks like they have actually invoked the circle-R registered trademark symbol.
It brings to memory those other legends like that post-war Japanese town that named itself "Usa" so that it could make products marked: "Made in USA"
http://www.snopes.com/business/genius/usa.asp
Looking back,I said I hadn't seen OEM until after the 1990s.
On reflection,I should have qualified it by saying I hadn't heard it used in the modern sense.
The old meaning of "OEM" was,where,say,Philips made a device "in house" & used it in their own equipment.
That exact device was not available elsewhere as a standard part----in other words,it was made by the "Original Equipment Manufacturer".
It has now morphed to the point that "OEM manufacturers" are those who make & sell sub units,or finished units to other companies to sell under their own brand,which is altogether a different shade of meaning.
"Badge Engineering" of this type has always occurred,but the terminology has changed.