What a sweet bike ! might be a bit later than mid eighties though, mainly due to the internal rear brake cable.
Here's a link to a 1990 bike that still had external rear cabling.
http://vi.ebaydesc.co.uk/ws/eBayISAPI.d ... 3&caz.html
Yours still has the curved forks so maybe up to early nineties, looking at the chainset (if original of course).
With that paint scheme though it could be as early as '88, and a master piu not a master. A bit of time on roadbike forums shows this:
http://www.bulgier.net/pics/bike/Catalo ... 88/04a.jpg
The master piu used internal rear brake cables a bit before the master did. The attached pic looks like yours.