Algeco and STS had 135 40T GLW Class A Petroleum tank wagons built by Metro Cammel and registered by BRM in 1963-4. The original number series was 501750 - 501884. They were hired to Carless Petroleum and carried many different volatile products. Later some were used by Whyte Chemicals Ltd, and were allocated diagram E661. Some were lagged and used for China clay see http://paulbartlett.zenfolio.com/ferryecctank.