Provincial Airways
Provincial Airways, who took over International Airlines route, flew their West Country Air Service between Croydon, Southampton and Plymouth. Mail bearing a label was carried for an additional fee of 3d, until the Post Office intervened.
25th November 1933. West Country Air Service.
Printed by Clark Doble & Co., Plymouth. Sheets of 4, bound in booklets of 5 sheets. Perf.: 11.
Orange and blue. Houses of Parliament, Liner leaving Southampton and Plymouth Hoe.

Five printings were made, each sheet being made up of four stereos clamped together. The first four printings used the original four stereos. There are colour variations between each printing and signs of wear in the later printings. The fifth printing was made from new stereos, and used red ink instead of orange.

Provincial Airways West Country Air Services Air Mail Magazine Volume 1, pp. 29-30, A. Phillips (1939)
The Air Mails of the British Isles Chapter 5, H. Stanley Redgrove, Privately Printed, (1940)
Provincial Airways' West Country Air service D.C.D. Potter, The Cinderella Philatelist Volume 7, October 1967, p. 75
Proofs of the Provincial Airways Stamps British Private Post Study Group Newsletter No. 5, October 1978 p. 18
Proofs of Provincial Airways Stamps Chris Tennant. British Private Post Study Group Newsletter No. 6, January 1979 p. 6
The Story of the Airway Letter Service 1933-1988 D. Wilson, Air Mail News June 1994