I was on the hunt for British and Commonwealth 'Pocket Field Service Pocket Books' and came across this great site with a great deal of info, not only of the Vickers MG, but of all sorts of other goodies. Worth a browse...
vickersmg.blog
The Vickers Machine Gun
An in-depth study of the Vickers MG in use around the world throughout the 20th Century.
vickersmg.blog