William Parker of London, is listed as supplying "COMPLETE ARMS 1804-1818" and "ROUGH STOCKER & SET UP 1820-1821, 1824-1827, and 1836-1839" in De Witt Bailey's British Board of Ordnance Small Arms Contractors.
Forgot to add the following from De Witt's book on page 58;
Parker supplied: "Infantry rifles and pistols in 1821, Pattern 1823 Infantry Rifles only 1824-1827, 16" Cavalry Carbines for the Queen of Spain in 1835-6, carbines, pistols, infantry rifles for the Shah of Persia, and Irish-service carbines 1835-9."