My vote also goes to 1980s. I would have guessed later than '83, but that serial number has me wondering.
The ones that Owen described above, with the different housing design - were those the ones that didn't have a carpet height adjustment, or were there three? (That description sounds more like a Vorwerk or Lindhaus to me, but I'll trust his account - there are lots of weird designs out there)
If there were three, then 1983 is probably too early, unless the new housing but without height adjustment was very short-lived. But "West Germany" puts it firmly pre-1990, unless some units still shipped from unified Germany marked thus.