There is a full-page advertisement from the British agent for Friedrich Fischer of Vienna, The Norse Trading Co (London) Ltd, in the 1937 British Journal Photographic Almanac:
In the New Goods section of the same issue, the Simplex tank is described but with an apparently different British agent:
THE SIMPLEX DAYLIGHT DEVELOPING TANK. (Sold by Westminster Photographic Exchange, Ltd., 24, Charing Cross Road, London, W.C. 2.). The Simplex tank is constructed entirely in moulded bakelite, it is for 3¼ x 2¼ films, and is capable of being loaded and operated throughout in daylight. It is so constructed that as the covering paper of the film is drawn away through a light-trapped slot from the outside, the film threads itself on to the spiral inside the tank. In the lid is the aperture for filling the tank with the necessary solutions and into which a thermometer can be placed. The whole sequence of operations of developing, rinsing, fixing, can be done in the tank, but washing is recommended to be carried out in a separate container. The capacity of the tank is approximately 17 ozs. and its price is 37s. 6d.