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1803 Dissolution of the Copartnership between David Evans, John Ambrose, Richard Cunningham, and Thomas Williams, called the Union Iron Company, carried on near Merthyr Tydvil and Abergavenny, but within the County of Brecon
1804 Dissolution of the Partnership between Richard Crawshay, Benjamin Hall, Watkin George, and Richard Cunningham, trading under the Name and Firm of the Union Iron Company. All persons indebted to the said Company are requested to pay the balance of their Accounts to Messrs. Crawshay and George at Cyfaithfa
1825 "Sale of Estates and Iron-Works in the Counties of Monmouth and Brecon.
.... in a Cause wherein George Price Watkins, plaintiff, and George Maule and others are defendants, .... the particulars herein referred to:
A freehold estate, in the Parish of Bedwelty, in the county of Monmouth, called the Rumney Estate, late the property of Benjamin Hall Esq., deceased, whereon iron-works have for many years been carried on, under the firm of the Union Iron Company, together with the furnaces, fineries, and other works thereon, including the machinery and stock, and fifty-two workmens' houses belonging thereto, and the foundations laid, and preparations made for additional furnaces and other works..."
Not sure whether this is the same company:
1855 Dissolution of the partnership between Alfred Goold, Timothy Bennett, William Bishop, John Hirst, John Broad, in Her Majesty's Forest of Dean, in the county of Gloucester, carrying on the trade or business of Malleable Iron Manufacturers, under the firm or style of the Union Iron Company.