Can you help identify a 20ft. open dinghy ?

[kds]

A friend is storing a dinghy for someone who no longer answers letters or messages.
I can't identify it. Perhaps built in '70 or '80s ? in GRP.
20 ft. long, narrow, almost canoe-sterned, open, long cockpit, sloop rig. The keel and rudder both wind up on a screw, leaving a flush, round bilge hull . No makers plaque or number on it. It might almost have been designed for handicapped people to sail ? (a wild guess !)
Not a racing class that I know. Any ideas which might point me in the right direction would be appreciated.
ken