Royal Army Service Corps
The Royal Army Service Corps (RASC) was initially known as the Army Service Corps (ASC), Royal being added to the title in 1918.
The first ASC units were sent to India in May 1916 (arrived June 4th) at a time when it was thought that the Indian equivalent, the Supply and Transport Corps, was not up to scratch – "The war in Mesopotamia quickly proved the shortcomings of the organization … for a campaign of this magnitude where the conditions differed from the accustomed ones. It was just after the fall of Kut el Amara that it was decided to send some Army Service Corps units to India."
Army Service number prefixes
With the renumbering of the Army in 1920, RASC numbers were prefixed S (Supplies), T (Transport), [Horse Transport], M (Mechanical Transport) or R (Remounts). 
During the First World War, there was a wider range of prefixes. The same prefix could have different meanings, but those relating to the Army Service Corps included
- M: M - Army Service Corps: Mechanical Transport; M1 & M2 - Army Service Corps; M2 - Army Service Corps: Electricians; MS – Army Service Corps: Mechanical Specials; MT – Army Service Corps: Mechanical Transport.
- R: R - Army Service Corps: Remounts; RS & R/TS - Army Service Corps: Remount Specials; RX - Army Service Corps Army Remount Section.
- S: S - Army Service Corps: Supply Branch; S - Army Ordnance Corps; S1, 2, 3, 4 - Army Service Corps: 1st/2nd/3rd/4th New Armies Supply (S4 Labour); SS – Army Service Corps: Supply Special (butchers, bakers, clerks etc); SRMT – Army Service Corps: Special Reserve Motor Transport.
- T: T - Army Service Corps: Horse Transport; T - Army Ordnance Corps; T1 & 2/ (SR) - Army Service Corps: Enlisted Special Reserve for New Armies; T1, T2, T3 & T4 - Army Service Corps: Horse Transport; TS – Army Service Corps: Transport Specials (trade); TSR – Army Service Corps: Transport Special Reserve.
The Royal Army Service Corps Volume II, by Col R H Beadon 1931 contains a chapter "The Corps in India" – Chapter XV, pages 457-486. Refer Historical books online, below.
Mechanical Transport Companies from Burma WW1
Main article: Burma Mechanical Transport Companies, RASC
Two Mechanical Transport Companies driving Ford Vans were provided by the Government of Burma, the Rangoon raised No. 1 Burma Ford Van Coy (1023 MT Coy ASC), and No. 2 Ford Van Coy (1024 MT Coy ASC). The 1st Burma Company had one third Indian drivers and all British artificers, whereas for 1024 MT Company, the whole of the drivers were Burmese, and the workshops had a great majority of Burmese artificers.
1023 Company departed Rangoon for Mesopotamia on 5 January 1918, and 1024 Company later, the latter arriving Basrah in July 1918. 
The Companies were based in Mesopotamia, and at least 1024 Company also including Mesopotamian Kurdistan, where there were some General Service Medals with the Kurdistan clasp awarded. 
There are surviving War Diaries at the National Archives, refer below.
It appears there were five Burma Ford Van Companies in Mesopotamia, refer External links below, and perhaps seven  in total.
Some of the Medal Index Cards at the National Archives refer to (Burma) Mechanical Transport, without mention of the Company number. The majority of these records are classified as Indian Army, although all ASC companies are believed to be part of the British Army.
Indian Mechanical Transport Companies
The following ASC Companies were renumbered Indian Mechanical Transport Companies, I M T on 6 May 1921.
- 630 ASC became 26 (Indian) MT Coy;
- 656 became 27 (Indian) MT Coy;
- 692 became 16 (Indian) MT Coy;
- 693 became 21 (Indian) MT Coy;
- 694 became 22 (Indian) MT Coy;
- 789 became 33 (Indian) MT Coy;
- 1028 became 34 (Indian) MT Coy;
- 1091 became 28 (Indian) MT Coy.
These units were officered by the Royal Army Service Corps but the rank and file were Indian.  Subsequently these units were transferred to the Indian Army Service Corps.
War Diaries at The National Archives
- WO 95 War Diaries, see First World War - The National Archives
- The TNA pay downloads available include the very informative "List of Royal Artillery, Army Service Corps, Machine Gun Corps and Medical Units" WO 95/5494. 
- WO 95/5390 War Diaries: North West Frontier Force contains
- 1028 Mechanical Transport Company ASC 1919 May – July
- 630 Mechanical Transport Company ASC 1916-1918
- 656 Mechanical Transport Company ASC 1919
- 692, 693, 694 Transport Company ASC 1915-1918
- 871 Mechanical Transport Company ASC 1917-1918
- Mesopotamia, Iraq and North Persia
- 1023 Mechanical Transport Company ASC WO 95/5007/3 1917 Oct - 1920 Apr
- 1024 Mechanical Transport Company ASC WO 95/5008/1 1918 July - 1919 Feb Note: Diary for Oct 1918 not included; and WO 95/5008/2 1919 Mar - 1919 Nov.
The flash, also known as a pagri (puggaree) badge, was generally affixed to the pagri on the sun helmet. The ASC flash was blue and (golden) yellow, the AOC red, blue red.
- Royal Army Service Corps Wkipedia. Retrieved 16 August 2014
- The Royal Logistic Corps Museum The Princess Royal Barracks Deepcut Surrey.
- RLC [Royal Logistic Corps] Digital Archive. A pay website. The RLC Digital Archive is a searchable pay-per-view or subscription archive containing digital images of a number of documents and books held in the Corps Library and also in the Museum.
- It contains the Gazettes and Journals from the Corps which merged to form The Royal Logistic Corps in 1993, Including the Royal Army Service Corps (journals from 1891) and the Royal Army Ordnance Corps (journals from 1906).
- It also contains Enlistment Book records from 1920 for the Royal Army Service Corps [Army nos. 1 - 57000, excluding 50001 - 51000] and the Royal Army Ordnance Corps [Army nos. 7574000 - 7581500]. Note: The enlistment register from 1918 containing a 'block' within the renumbering carried out by the RASC that year is missing.
- 801 MT COY ASC 801st Mechanical Transport Company of the Army Service Corps in Salonica and the Balkans.
- Photograph: Persia. 1918. A convoy of over ten Ford vans formed up ready for departure Unnamed Company. Australian War Memorial
Historical books online
- With the M. T. in Mesopotamia by Brevet Lt.-Col F W Leland RASC 1920 Hathi Trust Digital Library. (M.T.= Mechanical Transport, part of the Royal Army Service Corps)
- The Royal Army Service Corps: A History of Transport and Supply in the British Army, Volume II by Colonel R H Beadon 1931. Archive.org, Public Library of India Collection. Includes the First World War period, with chapters on the British Expeditionary Force, Gallipoli, the Balkans, including a section on the Army of the Black Sea; Egypt and Palestine, Mesopotamia, East Africa, Italy, North Russia, England and India.
- The Motor-Bus in War: Being the Impressions of an A.S.C. Officer during Two and a Half Years at the Front by A. M. Beatson (Temp. Lieut. A.S.C.) 1918 Gutenberg.org. The author was an Army Service Corps officer in the Mechanical Transport Supply Column of an Indian Cavalry Division. Elsewhere, the ASC company is recorded as being the 1st Indian Cavalry Division Supply Column which was 89 Coy ASC.
- Page 284 and page 285 "Appendix G: Mechanical Transport units raised in India since the outbreak of war", India’s Contribution To The Great War "Published by authority of the Government of India" 1923. British Library Digitised Manuscripts. Includes a listing on page 285 of five Burma Ford Van Companies raised for service in Mesopotamia.
- michaeldr “Army Service Corp, Bangalore 1918” Great War Forum, 16 September 2011. Retrieved 26 February 2019.
- New British Army numbers issued in 1920 renumbering longlongtrail.co.uk
- Army number prefixes “Army Service Numbers 1881-1918”
- Lindsay, Kimberley John. Operations in Mesopotamian Kurdistan, May to June 1919 Great War Forum 14 December 2015. Note you need to be logged in to the GWF to be able to view the information in the attachment. Retrieved 26 February 2019.
- Page 188 A Burmese wonderland : a tale of travel in Lower and Upper Burma by Major C M Enriquez, 3-70th Kachin Rifles, Divisional Recruiting Officer, Burma 1922 Archive.org
- Army Service Corps 1902-1918 by Michael Young. This information was kindly provided by Noel Clark.
- Matthew B "IMT, Unusual Regiment?" Great War Forum 11 June 2014. Retrieved 26 February 2019.
- WO 95/5494 List of Royal Artillery, Army Service Corps, Machine Gun Corps and Medical Units with the Division, Corps or Army they fought with. The National Archives.
- FROGSMILE. Help needed ID-ing unit flash on pith helmet Great War Forum 30 May 2011. Retrieved 26 February 2019.
- FROGSMILE Tracing Casualty Rolls in Newspapers Great War Forum 23 September 2015. Retrieved 26 February 2019.
- Larkin, Roy. The Motor-Bus in War. A.M.Beatson , 1918 Historic Military Vehicle Forum 8 February 2015. Retrieved 31 January 2016.