Records of the Ystradgynlais and Swansea Colliery Company, 1803-1936, comprising minute book of meetings of directors and shareholders, 1874-1936, share ledger, 1874-1886, and deeds and documents of the company, relating mainly to the Ystrad-fawr estate, Ystradgynlais, Brecknockshire, 1803-1903.