Thanks to all who suggested ways to remove the epoxy from the underside of the bottom bracket shell where the plastic cable guide was attached.
Heat did the trick - soldering iron, sharp screw driver and wire brush.
Also took some lacquer thinner and soft rags to the frame, looking in all the likely places for decals under the black spray paint and primer, but none remain on the original orange paint.
Anyway, the serial number is:
84C11)83.
The ")" represents a character that I can only describe as a backwards "C"
Hope this is enough to ID it!
Ann Phillips Atlanta GA - rainy and cold and making my day off totally unsuitable for riding.