Isn't "Sheen" a line of Casio watches?
Yes, but I don't think they where produced in the early 70s, quite a bit more recent I think.
Maybe it was a special promotion by Mr Sheen the furniture polish manufacturer.
Thinking about it it might not be as daft as it sounds, if Gillette (shaving foam and razors) can produce several different 'reflex' models and 'Boots' (Chemist\Pharmacy) can have their own brand of watches then why not Mr Sheen.
We had a long running TV advertisement here in the UK which had the catch phrase .....'Mr Sheen gets everything clean.' maybe they tagged along 'and tells the time too.'