John Howkins Antiques has dated this piece to the 1800s.
The blunderbuss retains the original steel ramrod and brass fittings with walnut stock chequered carved grip and signed “BECKWITH”. Condition- very good and original. Dimensions:- Length Closed…31.5’’/ 80cm. Length inc Bayonet…44’’/ 112cm. Width…2.5’’/ 6.5cm. Depth…8.75’’/ 22cm. Free U.K. delivery on this item.

Literature ref. - Howard L. Blackmore (1986) Gunmakers Of London, 1350-1850. George Shumway Publisher. USA.
Apprenticed to Wattell Clark, 1785; free of Gunmakers Co., 1801. Elected Assistant (and Livery) 1805; Master, 1808, 1814, 1825, 1840. Died 1841. Gunmaker, 58 Skinner St., Snow Hill, 1802-41. 125 Strand, 1818-2. Contractor to Ordnance, 1838; East India Co., 1823-41. Business continued at 58 Skinner St., by Widow Elizabeth 1841-68. Contractor to East India Co., as Elizabeth Beckwith & Son, 1842-53.
John Howkins Antiques has dated this piece to the 1800s.
You can view the stock and full dealer information on the John Howkins Antiques Profile Page