With that serial number, it would either be a 1970 or a 1980. Without a picture, it's difficult to say which it is, but odds are 1980.
Mechanicsburg, PA, USA
> From: Wayne Davidson <firstname.lastname@example.org>
\r?\n> Subject: [CR] dating my team Raleigh track bike frame
\r?\n> To: "CR" <email@example.com>
\r?\n> Date: Sunday, February 22, 2009, 6:09 PM
\r?\n> Hi all, after trolling the net, is it safe to say that my
\r?\n> serial number, WM0006677 4 means that its made in Worksop in
\r?\n> september of 1976 and is #677?, the 4 I've not been able
\r?\n> to ID that, if you want a pic I'll take
\r?\n> one............regards wayne davidson Invers NZ...........