http://mediasvc.ancestry.co.uk/v2/image/namespaces/1093/media/2efa2fe2-7ffe-41cf-adfa-5532df77763a?client=TreesUI
Think it is from around 1880-1890 and British.
Do you have any more information about your great-gradfather? If you have anything about what he did during his service, that would probably help narrow it down a little more.