Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
In my experience it is not unusual for a vehicles manufacturing date to differ by be as much as two years from the date of first registration due to being unsold new stock during that period.I am not sure from the brief details you have given what country it was first registered in if it was the Netherlands then when imported to the UK DVLA would use the data from the foreign registration document.
I thought the earliest ones/ 1979 - had single disc/ wire wheels. But would need to dig around online a bit to check if that's the case.
Yep here it ishttp://www.sohc4.com/cb550/cb650/