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There never was a white Kirby bag. It's a gray bag that is very faded. It's hard to say which specific model this is.
The fan housing has the rounded-off edges like the 4C and then the 505~513. (The edges of the fan housing on the 3C and earlier were sharper.)
It has the old-style toggle switch, meaning it wouldn't be newer than a 512. (The new "push-push" switch was introduced on the 513.)
At first, I thought it had a wooden handle grip which was odd, since that style ended with the 2C. (The 3C was the first model to have a rubber grip.) But in looking more closely I realized it's the handle style with the rubber grip but the rubber is gone, leaving just the bare metal underneath.
So it's either a 4C or a 505 through 512.
But any way you look at it, it's a pity it was just discarded.