Anybody know when Kirby started using bag guards around the emtor? The older machines that I have seen pictures of, 505, 508, 509,etc.. didn't seem to have them. Just curious.
The first model to use a bag guard was the 516, which Kirby called "The 50th Anniversary Kirby" [see link].
They went all-out on a total redesign of the motor housing and color scheme, including a red bag guard originally made of the same red rubber material as the belt lifter bumper, but then soon was switched to vinyl. Probably the rubber stretched out too soon so the switched to a more durable and less stretchy material.
Then, somewhere along the way, the headlight bumper was also made of red vinyl, as was the flexible hose (which also was originally made of rubber).
As I note in my "Kirby 500 Series" pages, these zillion little differences between various Kirby 500 machines came gradually and not necessarily in consecutive model outputs -- e.g., you might find an early 517 with a smooth center handle section and a later one with a ribbed handle, etc. etc. The same goes for the materials used for trim etc.