Gave the 510 back for a display item (even though it runs great) since I already have a 510. Today I was offered a Kirby Sanitronic VII for free and said no thanks, since I already have one.
That's pretty cool! I actually was given a 505 for free (without speed switch) from my local Kirby dealer in 1990, if only I hadn't taken it apart a few years later. . .