The 38th (1st Staffordshire) Regiment of Foot officers button.

Officers 25mm button in immaculate condition with a gilt finish and a Firmin backmark. The condition is exceptional for something of that age.​​​​​​​​​​​​​​​​

The 38th (1st Staffordshire) Regiment of Foot was an infantry regiment of the British Army, formed in 1705 and amalgamated into the South Staffordshire Regiment in 1881.
The regiment was raised by Colonel Luke Lillingston at Lichfield in 1705. Its first posting was to Ireland, and then in 1707 it was sent to the West Indies, where it served as land troops and marines for 57 years, mostly on Antigua.
The regiment saw service in the American Revolutionary War, the Napoleonic Wars, the Crimean War, the Indian Mutiny, and a number of smaller colonial campaigns. It fought at the Alma, Inkerman, and Sevastopol during the Crimean War, and took part in the capture of Lucknow in 1858 during the Indian Mutiny.
Under the Childers Reforms it amalgamated with the 80th Regiment of Foot (Staffordshire Volunteers) to form the South Staffordshire Regiment in 1881. 
The rope/wreath device at the bottom of the button face is a traditional decorative element associated with the regiment’s design.
Dating the Button
The backmark reads “FIRMIN & SONS Ld LONDON” – and this is where it gets interesting for dating. Firmin & Sons became a Limited company in 1875, and the abbreviated “Ld” backmark (as opposed to the full “LTD”) was used from 1876 to 1894, after which the company moved from the Strand to St Martin’s Lane.
So this button dates from 1876-1881 . 25mm in immaculate condition with a gilt finish and a Firmin backmark, it’s a very presentable example. The condition is exceptional for something of that age.​​​​​​​​​​​​​​​​