Outstanding piece of creative and lateral thinking and research source finding,...a fantastic find, and particularly so as Kew, in common with many such National Archives, is frequently a daunting puzzle palace of a place to search, even just navigating around the Kew site is a pretty nebulous task.
http://discovery.nationalarchives.gov.uk/SearchUI/Details?ur...Not so sure that it might be necessary to poke around in all of the 5456 boxes files and volumes, and anyway that would be a pretty impossible task, there must have been some form of indexing in use, both for the files of individuals, and for the archives of the various departmental files at Kew.
For male conscripts, there may have been local medical boards in use in different towns and cities and within different local areas within London.
That certainly seems to have been the case in regard to female conscripts.
http://discovery.nationalarchives.gov.uk/SearchUI/s/res?_q=M...http://discovery.nationalarchives.gov.uk/SearchUI/s/res?_q=M...A poke around in the related Ministry of Labour records might be productive as well.
http://discovery.nationalarchives.gov.uk/SearchUI/details/C7...http://discovery.nationalarchives.gov.uk/SearchUI/s/res?_q=l...75 year file closure rule, well, it ain't always necessarily so.
Such closure time period rules would have been set for files at the time when they were originally deposited at Kew, but things have moved on since then, and rules and laws have changed.
Subject to the various exemption rules that apply to various files, access to some otherwise time closed files may sometimes be granted upon application, at least to files with a direct family connection, and especially so if the individual to whom the files relate is now deceased, and also if there is not deemed to be any breach of personal privacy in granting access to their files.
http://nationalarchives.gov.uk/foi/default.htmhttp://www.justice.gov.uk/information-access-rights/foi-guid...http://nationalarchives.gov.uk/help/accessibility.htmhttp://nationalarchives.gov.uk/legal/our-fees.htmhttp://discovery.nationalarchives.gov.uk/SearchUI/details/C7...Be warned though, if you poke about too much in the Kew archives, and get too familiar with their records and archival file systems, you may end up as an anorak.! :):)
The furniture, textiles, and fashion, department of the Victoria and Albert Museum in London might be able to give you an opinion on the identity of the regalia in the photograph.
http://www.vam.ac.uk/content/articles/f/furniture,-textiles-...DOM and KOM might be, Dame and Knight of the Order of Malta.
Although I doubt that in your situation it will be relevant or apply to the context of the following Roman Catholic organisation, but it may well be applicable in the context of Freemasonry.
aka The Sovereign Military Hospitaller Order of Saint John of Jerusalem of Rhodes and of Malta
Basically a Roman Catholic lay organisation with connections to medical and first aid services, but with historical chivalric origins.
http://en.wikipedia.org/wiki/Knights_HospitallerA British branch called the Venerable Order of Saint John aka The Most Venerable Order of the Hospital of Saint John of Jerusalem was the founder of the St John Ambulance Association.
http://en.wikipedia.org/wiki/Venerable_Order_of_Saint_JohnFreemasons do a have a male masonic Knight of Malta degree, and they do wear gauntlets and aprons with KOM on them, the lodge name may also be present but it may not be legible on your photograph, the medals might also be useful clues.
http://en.wikipedia.org/wiki/Knights_Templar_(Freemasonry)#T...Did they also have a female Dame equivalent ?,...I don't know.
It might also be, the Buffs, aka the Royal Antediluvian Order of Buffaloes, although I'm not sure if they used to have women members back then, but they do have a male degree called a Knight of Merit.
http://en.wikipedia.org/wiki/Royal_Antediluvian_Order_of_Buf...Of course there were many other such organisations with similar regalia and terminology.
http://www.freemasonry.london.museum/showcase/other-societie...Your best bet would be to try and scan and post the picture, or to refer it to the Library and Museum of Freemasonry in London
http://www.freemasonry.london.museum/http://www.freemasonry.london.museum/contact-us/