This guitar was recently identified as a modified Burns Nu-Sonic from the mid-1960s. It look like the pickups have been changed (the original single-coil units would have been covered with black plastic bearing the legend: "Burns Nu-Sonic" in white printing).

It also looks as though the tremolo bar has been changed - it's still a Burns arm (possibly from a later Marvin or Bison) but not the correct one for the model. See: http://www.vintageguitar.com/brands/details.asp?ID=111 where the Nu-Sonic (not to be confused with the earlier Sonic model) is mentioned. The instrument had been discontinued by mid-1966.

The same guitar was distributed in USA by Ampeg as the "Sonic Six", see http://members.aol.com/bluemuse/instruments.html

Identification credits:
Jim Nugent, UK.
The owner:
Roberto, Spain.