First names that popped into my mind is Joseph Manton & Son. Here's what I found in Vol. 1 of John Blackmore's Gunmakers of London:
Charles, Son of Joseph, b. 1806. Learnt trade with father, probably went to India where Manton & Co. was founded. Apptd. Master Furbisher, Tower of London, 1829. His cavalry carbine adopted by British Army, 1833; nipple key approved by Ordnance, 1835. Resigned and emigrated to Australia, 1840.
Edward Son of John b. 1796. Sent to India, managed Manton & Co., 1834-46.
John Augustus. Son of Joseph, b. 1809. In Calcutta with Manton & Co., 1828-33. Granted Eng. Pat. No. 6572 (Percussion wooden-plug lock), 1834. Lock tried by Ordnance, 1835-6 (Blackmore 2). Traded as Joseph Manton & Son, 1834-8. Imprisoned for debt, 1836. Emigrated to Australia, where d. 1852 (Neal 3).
Manton & Co. Gunmakers established in Calcutta, India by Frederick Manton, c. 1825. Managed by John Augustus Manton, 1828-33; Edward Manton, 1834-46; Purchased by W. R. Wallis, 1846. London office, 116 Jermyn St. Firm still in existence.
There were many more Mantons in the trade & the family began gunsmithing in the flintlock era (right after the Seven Years War - 1768). Suggest you contact the curator at the Smithsonian or the Frazier Arms Museums (Louisville, KY).
from Vol. II of Blackmore's Gunmakers of London Supplement, p 85-86:
Joseph I, Brother of John, b. 1766. Served appr. with brother. His new method of rifling cannon and loading (with cup wads) tried but not adopted by Ordnance, 1790. m. 1792 (SGH). Gunmaker, 25 Davies St., 1791-1807; 24-25 Davies St., 1808-10; 27 Davies St., 1811-18; 11 Hanover Sq., 1819-26; 315 Oxford St., 1820-26. Two workshops at 25 Davies St.; a house (with Elizabeth Jones), 3 Carpenter St., Grosvenor Sq., 1806 (Sun. Ins. Nos. 787354/5, 795413). The property at 25 Davies St. Housed a shooting gallery frequented in 1814 by the Lords Byron, Yarmouth, Blanford, etc. (Reminiscences & Recollections of Capt. Grenow, 1892). In 1820 his insurance policies show that, in fact, he still occupied 25 Davies St. as well as workshops at 11 Hanover Sq., and that he apparently owned houses at 131 New Bond St.; 4 Market St., Mayfair; 9 Somerset St., Portman Sq.; Great Ormond St.; 1 Mount Row; with several other workshops, coach houses, a chapel and a brewhouse with a total value of 11,650 pounds (Sun Ins. Nos. 926817/8). By 1824 his address is given only as 11 Hanover Sq. but he still insured 131 New Bond St. then in the tenure of Hayward a tailor (Sun Ins. No. 1021095). He was declared bankrupt, 1826. New business at Marylebone Park House, New Rd., 1827-28. Imrpisoned for debt, 1828-29 (Neal 3). At Burwood Pl., Edgeware Rd., 1831-32; 6 Holles St. (with son John Augustus), 1834-35. Gunmaker to East India Co., 1796-99. Gunmaker-in-Ordinary to George IV, 1820 (LC 3/69). Granted Eng. Pat. No. 1865 (Improved hammer), 1972; No. 183 (Improved trigger and cup wads), 1792; No. 2722 (Hammer with air escape), 1803; No. 2966 (sighting ribs), 1806; No. 3558 (waterproof breech & gravitating stop), 1812; No. 3985 (Pellet Lock), 1816; No. 4166 (Improved flintlock), 1817; No. 4285 (Percussion-tube lock), 1818; no. 5106 (Magazine primer), 1825; No. 5135 (Lead shot), 1825. Also patents for "timekeepers working in vacuum," 1807 and air-tight telescopes, 1810. His trade label also cliamed 'Inventor of Platina Touch Holes." d. 1835. Buried Kensal Green Cemetary. Admin. granted to sons John Augustus and Charles (PCC).
