GLEN SANNOX was the last and by far the largest of the 1950s built car ferries to operate on the Firth of Clyde. She was completed in 1957 by the Ailsa yard at Troon and even then was described as a block of flats owing to her high accommodation.
She operated on the Ardrossan to Brodick service of the Caledonian Steam Packet Company until approximately 1969/1970 when she was displaced and overtook other routes, such as Rothesay where I took this in 1971.

IMO added, thanks to P.F. Kerr
(JS)