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Typed in black ink on off-white paper. 'Powell Duffryn House' headed paper. A letter to E.Ivor David regarding the change-over of the compressors at Bargoed from steam to electrical drive. Dated 17 December, 1955. Loose within a beige/light brown file containing copies of the 'Metcalf papers' and documents relating to the 'Conversion of Turbo Compressor to Electrical Drive'.
