'DIOPTRIC SURVEYOR'
No IMO

July 1985, Dock Basin, Port of Felixstowe, England.

Completed in May 1967 by J. Bolson & Son, Hamworthy, England (556)
154 g.t., as:
'Sir John Cass' to 1985,
'Dioptric Surveyor' to 1986,
and with unknown name & status since.

An interesting history, designed and equipped for radar training and marine research for The Sir John Cass Nautical School, London.
One of the first vessels to be built specifically for this dual purpose.

MV 'Sir John Cass' was sold in 1984 by the City of London Polytechnic, and the ship was re-named, the Trinity House Vessel 'Dioptric Surveyor'.

During this time, it was widely reported that she was actually in use as a 'spy ship' for the DTI (Department of Trade & Industry) in the North Sea, for the monitoring of several Pirate radio ships.
The ship was then sold in 1986 to the Turks & Caicos Marine Archaeological Recovery Ltd.

I can find no trace of a subsequent name or location since.