in Handsworth, Birmingham
1788 Boulton approached the British government with a proposal for minting low value coins by machine, as an improvement on the hand-made process then in use. This would help to alleviate the shortage of copper coins in Britain and would cost less. Samples were available in May although the first order from the government did not come for 10 years. Boulton built the first steam-powered mint, adjacent to his manufactory at Soho (grid reference SP051890) in Handsworth, near Birmingham, taking sheet and strip copper from there.
Note: Boulton & Watt's Soho Foundry was a separate business, located 1 mile west of the Soho manufactory and Soho Mint.
Business in manufacturing coins, medals, tokens and mint machinery came from the colonies and elsewhere. The mint contained eight machines, driven by steam engine, each capable of striking 70 to 84 coins per minute.
In addition to copper domestic coins, silver coins were made for some of the colonies, and various medals were struck, a grand total of 600 million.
1809 After Matthew Boulton's death, the Mint was directed by Matthew Robinson Boulton.
1841 MRB's son Matthew Piers Watt Boulton took over from his father until it closed in 1850
1850 On 1 April, the auction was announced of equipment from the defunct Soho Mint.
There are no remains of the Soho Mint or the Manufactory to be seen above the ground.
1850 'During the past week Messrs. Fuller and Horsey, auctioneers of London, have been engaged in disposing of the machinery, dies, coins, and medals of the Soho Works, near this town. The auction commenced on Monday last, by direction of the executors of the late Mr. Boulton, and was continued daily until Friday evening, when it closed with the 707th lot. The well-known celebrity of the Mint and other departments of the manufactory attracted a great concourse of machinists and others to the sale, and the competition for many articles was very spirited. The collection of dies was secured principally for Sir George Chetwynd, and Mr. Makepeace, who, it is presumed, represented Mr. Boulton. Some of them were afterwards re-purchased for France. The coining presses sold low, the highest prices being 75l. for lot 9 consisting of a press, highly finished, with 5 1/2-inch bright screw to rise 5 inches at one revolution, with steel plug, brass-box, 18 inches deep, cast-iron fly, and cast-iron balance-beam, 12 feet long. Lot 202, consisting of 119 medals and coins, struck at the Mint bronze, and including representations of the Emperor of Russia, Execution of the King of France, Queen Charlotte, tbe Battle the Nile, Lafayette, Rousseau, &c, sold for 6l. ...... Lot 341, a portable condensing steam-engine, 12-horse power, by Boulton, Watt, and Co., 185 guineas, purchased for Mr. Wilkes. Lot 549, a powerful medal, or multiplying press, purchased by Mr. Lingard, for 19l. 7s. The tools and machines sold well, considering the antiquity of their construction. The pumping engine, "Old Bess," the first constructed by James Watt, realized 52l. 10s.; purchased by Mr. S. Walker. This engine is a perfect curiosity, the piston-rod was made from broken Redditch needles, purchased by Mr. Watt for that purpose. Mr. Walker also bought another engine. The rolling mills and rolls were purchased by a London house for from 5l. to 12l. per pair. The present firm of James Watt and Co., purchased one of the coining presses and appendages.'
Some of the machinery was bought at auction by the new Birmingham Mint of Ralph Heaton II.
Recent Detailed Accounts
2010: A thorough study of the successful development of the Soho Mint by Matthew Boulton was undertaken by Sue Tungate for her PhD thesis, which is available online 
2022: The book 'The Soho Manufactory, Mint and Foundry, West Midlands' by George Demidowicz provides a comprehensive and profusely illustrated analysis of the Soho factories 
Sources of Information
- Aris's Birmingham Gazette, 6 May 1850
- 'MATTHEW BOULTON AND THE SOHO MINT: COPPER TO CUSTOMER' Ph.D. Thesis by Sue Tungate, 2010
- 'The Soho Manufactory, Mint and Foundry, West Midlands - Where Boulton, Watt and Murdoch made History' by George Demidowicz, 2022. Liverpool University Press for Historic England
-  Wikipedia
- The Lunar Men, by Jenny Uglow, Faber and Faber, 2002