This was a fairly common model back in the day, so I wouldn't think it was too rare. Vax machines were often relegated to the garage (when the lady of the house found out they were hard work to use as a daily driver), and with only occasional use to wash carpets or vacuum out the car, they end up soldiering on for years. So there are probably far more of them still about than even we would realise!
Originally this would have come with the clear wash head. The Ultra Rapide head included in the listing would have been purchased as an optional extra, and later when it became standard equipment the machines themselves were branded Rapide to reflect this. After that, Vax obsoleted the clear wash head, and the Ultra Rapide was offered as the alternative spare part. I think it's the best of the bunch; the original wash tool worked great but was hard work to use on some carpets, while the current style is just craptastic in general.