Karl,
Some vac suppliers may have contracted with Kirby and others to sell trade-ins that were "re-furbed". The idea is to use the overstock of parts (and colors) that have a limited life span and put them together to make a useful, working, new machine. Most people wouldn't know the difference and much less care. A number of factors could come into play here. As mentioned above, Hesco sold the LIKENESS of a Classic III for $149 just a few years back. I am willing to bet that they weren't all Classic IIIs from the start. I guess it's kind of like a "trans-vac" LOL!!
Simply stated, a Hoover convertible is a Hoover convertible just as a Kirby is a Kirby is a Kirby. (no, this is not a miss type). Regardless of trim and color, it's the same machine and performs the same. One can take any two brand new(exact same models)Kirbys or Hoovers (or any other brand for that matter) right off of the assembly line and no two would be exactly alike and/or would have the same cleaning efficiency. In the manufacturing world these is a term that is used, called "manufacturing tolerances" which is an acceptable percentage of variances between units. And as I am writing this I may be wrong but I believe that I seem to recall Hoover using this word on some of their ad spec sheets years back. I have bought vacs in boxes a few years back and when I opened them and tested them, no two motors particularly sounded exactly alike - irregardless of brand! Some armatures are wound tighter than others as is evident by the motor pitch. Try it yourself! Buy two hand mixers and critically compare them. You'll see! Trust me!
Louis