Yes, the switch is clue that this may be a 513. (OTOH, see comments below.)
The first reference to the "push-push" switch in Kirby literature that I've come across is in a typewritten, mimeographed & stapled 8.5x11 booklet dated February 15, 1953. I've scanned the cover. (The brochure is 10 pages long; too much stuff to scan.)
Since this brochure was prepared in such a simplistic fashion -- looking more like a schoolteacher's project than official company printed matter for distribution to the publc -- my guess is that it was a small run for a limited number of people, perhaps branch managers and so on.
-ooOoo-
What some people may not realize is that when vac shops -- Kirby or otherwise -- tear down Kirbys for rebuilding, all the parts to one particular machine do not stay together. Rather, all the handle grips go in one bin, the forks in another, the headlight housings in another, the switches in another, the nozzles in another ... and so on. When a machine is put together for rebuilding, they just reach in the various bins for a handlegrip, a fork, a headlight housing, a switch, a nozzle, etc.
The exception to this is machines that are sent in for rebuilding under the orignal-owner warranties, the parts of a given machine are kept together.
