21st Regiment of Foot

Also known as The Royal Scots Fusiliers

Chronology

1678 raised as the Earl of Mar's Regiment of Foot ('Mar's Grey Breeks') also known until 1751 by the names of twelve other colonels
1685 became the Scots Fuzileers
1688 became the Royal North British Fuzileers
1751 became the 21st Regiment of Foot (Royal North British Fuzileers)
1877 became the 21st (Royal Scots Fusiliers) Regiment of Foot
1881 became The Royal Scots Fusiliers
1959 amalgamated with The Highland Light Infantry (City of Glasgow Regiment), to form The Royal Highland Fusiliers (Princess Margaret's Own Glasgow and Ayrshire Regiment)
2006 amalgamated with the other regiments of the Scottish Division to become The Royal Highland Fusiliers, 2nd Battalion, Royal Regiment of Scotland, abbreviated to 2 SCOTS

Royal Scots Fusiliers Wikipedia
Royal Highland Fusiliers Wikipedia
Royal Regiment of Scotland Wikipedia
The Royal Scots Fusiliers including deployments: 1st Battalion, 2nd Battalion Regiments.org, an archived site.
The Royal Highland Fusiliers Museum which includes a Library. Covers the 21st, 71st and 74th Regiments rhf.org.uk
"Gone For A Soldier: The Anatomy Of A Nineteenth-Century Army Family" by Derek J. Oddy, emeritus professor, Journal of Family History, Vol. 25 No. 1, January 2000 pages 39-62. Case study involving three generations of family members who served in the 21st Regiment of Foot/ Royal Scots Fusiliers .smu.ca
Photograph of the “Fusiliers” Band (possibly the Royal Scots Fusiliers) in Simla c 1930. FIBIS on Facebook

Historical Record of the Twenty - First Regiment or the Royal North British Fusiliers: containing an account of the formation of the regiment in 1678, and of its subsequent services to 1849 by Richard Cannon 1849. Google Books. Indian Service commences page 48 in Calcutta in 1839
Historical record and regimental memoir of the Royal Scots Fusiliers, formerly known as the 21st Royal North British Fusiliers. Containing an account of the formation of the regiment in 1678 and its subsequent services until June 1885 by James Clark 1885 Archive.org. Indian service commences page 43 in 1839 in Calcutta
"The Royal Scots Fusiliers" from The Lowland Scots Regiments : their origin, character and services previous to the great war of 1914 edited by Sir Herbert Maxwell 1918 Archive.org
The History of The Royal Scots Fusiliers 1919—I959 by Colonel JC Kemp is available to download as a Word Document (which depending on your browser you may find in your downloads folder - it then needs to be opened). Chapter 1 gives an outline of the 2nd Battalion in India 1920-1930, and a brief mention of the First Battalion in India in the late 1920's. Archive.org