Like it or not, the DA001 is now Vintage, as it is technically 20 years old. The DC01 is not yet vintage as the new style Dyson logo and the DC01 logo didn't appear for a few years after the DA001 was launched in 1993, although I'm not exactly sure when the new Dyson logo and DC01 name came out - possibly in 1995 or 1996?
I think the DA001 had a couple of differences mainly in the soleplate design to the DC01, but is essentially the same cleaner.
Its also hard to imagine the Purepower being classed as vintage as its still sold even now in the same design as it was in 1997.
The Kirby Generation platform is now vintage too, even though the Sentria 2 is essentially the same cleaner, with a few facelifts on the G3 which came to the UK in 1991
Has Dyson announced any 20th anniversary celebrations yet? Thinking about it, in 20 years he has completely changed the face of the vacuum cleaner industry, and as good as wiped out demand for bagged cleaners.
Citroen BX should never sell his DC01/DA001 machines as these, being in such good condition and also being the original Dyson machines from launch will be very collectible in years to come. He should of course try to keep them in the dark, as light exposure will continue to make the ABS more and more brittle.