No single published list of firms exists which could serve as a basis for a study of the heavy steel industry. The problem was to discover what firms are and have been ingot-makers since the first Bessemer converters came into use in the early 1860's.

The first firms to be studied were obtained from the Stock Exchange Official Intelligence or Yearbook. All firms which were described as steel manufacturers in the volumes for 1905, 1915, 1925, 1935, 1947 and 1953 were taken as a beginning. With the assistance of Professor Brian Tew and members of the staff of the British Iron and Steel Federation, all firms in this list which were not making heavy steel in 1913, and have not manufactured it since, were eliminated. For the most part the firms taken out made only electric or crucible steel or were re-rollers or pig-iron makers only.

Identification of firms which were ingot-makers before the public company became the dominant form of industrial structure required the use of more varied sources. Up to 1881 lists of firms making Bessemer or open-hearth steel appeared in Robert Hunt's Mineral Statistics for the United Kingdom, but the series was discontinued when the Home Office took over the publication of mineral statistics in 1882. The Iron and Coal Trades Review published lists of all firms making open-hearth steel in 1899 and 1903, and more firms were added from this source.