Jerry Mortimore (www.carltoncycles.me.uk) has a 1977 catalogue for Carlton, and it in that year, they went to block CARLTON logos the seat-tube, downtube, and forks, and dropped the lagoon-blue color (which was also dropped from the Raleigh-Carlton lineup, too.)
The mid-70's catalogue here :
http://spokessmann.tripod.com/
is actually the last few pages of a Raleigh catalogue, so the high-end models are not included. I have this catalogue, plus a similar one, both are mid-70s catalogues +/- 1 year.
If your bike has bocama lugs (like a Raleigh Gransport, which was offered in lagoon blue), then I'm guessing it could be a Carlton Kermesse, which is a mid-range bicycle, 531 forks and DB main tubes only. If your bike has Campagnolo dropouts, then it's probably a Professional model.
- Don Gillies
San Diego, CA, USA