Thanks so much for the quick response, thats really interesting.. its a matt black dial, full 'viceroy' colour scheme.
There are no markings on the rear but its been worn very regularly/serviced and 'cleaned' a good few times as it was the previous owners daily for quite a while (he purchased in the 80s). However the top and sides have not been ruined by polishing im pleased to say and ref numbers still very clear.
Sorry, rambling.. no sign of markings on caseback but its quite worn!
Its a Tachy bezel insert, bezel is good(ish) but insert quite knocked up.. i cant tell if its a genuine insert or replacement.
So, looks like a 1980/81 from your info. If there's anything else you think i should look for then please add.