Yes, that is a 1977 2618 alright, built in May (E77**** - E=May, 77=1977, ****=serial no.). The 2618 was a 24 fret neck and dot inlays, where most other models were 22 fret. Very nice guitars indeed, kind of like a maple capped SG.
For more info:
http://www.ibanezcollectors.com/ - Ibanez Collectors Forum
http://www.ivc.ca/misc/artist/ - Ibanez Artist Pages
Unfortunately, these guitars are becoming quite sought after by collectors, although original one's with their cases get the premium. Prices are pretty much the same in the US as the UK it seems (look at the collectors site), obviously traders/dealers/shops will charge a premium. If you do go for it, it's worth buying the original pickups as well (if you ever sell it on).
I have a stock '79 2619, which plays superbly, even sounds good!