I do that with all of my cleaners if I post pictures - I had my identity stolen in 2002 and I'm semi-paranoid about sharing anything that is uniquie. For example, my Sentria serial number I'd never share because it's registered to Kirby in my name. Same for the Dyson's I had, and my Miele S5s and S7.
As far as this Kirby, I'm not 100% sure of it's "history" so to speak, but that didn't stop me from buying it as it was new in the box. ;-) I'd rather not have that S/N public knowledge because of the uncertanty is all.
I'm going to probably do a video soon of the shampooer in action, as well as a carpet fluffer video, maybe even the turbo sander polishing my dining room table. Just need to find the time