While I can't give you a direct answer, I can guide you... the nice thing about KEF is they keep info on every product they've ever made.
Welcome to the KEF museum where you can find information on all loudspeakers manufactured since the company was founded in 1961. The archive is divided into decades, within which you will find thumbnail images of the products or product ranges of that period. Click on the thumbnails to go to a...
us.kef.com
I would suspect you will find those in the 90s or 2000s.
I'm at House 2.0 right now, with no Wi-Fi and no computer, so to would be a chore combing those links on a phone.