As far as I know, but not definite fact, the UK bikes never had the sticker after they began stamping the chassis number on the headstock as it wasn't a requirement, whereas in other countries I think they had to have more info than just the number. Similar to how some bikes that were sent to Italy, Germany, maybe elsewhere in Europe, had an additional chassis number begining DG. So someone may have imported the bike from elsewhere at some point. UK bikes had alloy tanks from 1973 onwards, everywhere else they had the original fibreglass tanks from the factory
Or maybe some UK bikes did come with the sticker, I don't know for sure, but never seen one other than on a MK1
