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Prager Maschinenbau-Aktiengesellschaft (Prague Mechanical Engineering Company) of Prague, formerly Ruston & Co.
The company had its roots in the engineering business started by Edward Thomas, which in 1850 became Ruston & Evans, and then, from 1854, Ruston & Co. Ruston & Co was established by Joseph John Ruston and his brother John Joseph Ruston. For more information, see Wikipedia entry.
The following information is condensed from Albert Gieseler's website
1869 Ruston & Co became Prager Maschinenbau AG.
1877 Takeover of the Josef Hartmann shipyard in Budapest.
1880 Purchase of Hartmann's shipyard and machinery factory in Budapest (later "Danubius")
1884 Aurel Stodola started his career as an engineer at Ruston in Prague, leaving in 1892.
1886 Making high-speed steam engines of the Doerfel-Proell type, developed by Prof. R. Doerfel and Wilhelm Rudolf Proell (10/02/1845 - 14/9/1892).
1887 Started making triple expansion engines.
1890 The former Hartmann shipyard was separated out as an independent company "Danubius, Ungarische Schiffbau und Maschinenfabrik AG".
By c.1908 the firm was trading as Prager Maschinenbau AG vorm. (formerly) Ruston & Co, Bromovsky, Schulz & Sohr. Sohr was Richard Sohr. See photograph of single cylinder horizontal steam engine, with refrigeration compressor, at Vienna Technical Museum. Used until 1977 for ice making at Mainz Hospital. 25 HP, 240 mm bore, 400 mm stroke.
At another time the firm was called Prager Maschinenbau Aktien-Gesellschaft (vormals Ruston, Bromovský u. Ringhoffer), Prag.