Perhaps the rank or regiment could be identified from the collar or helmet by specialists at the National Army Museum or an online community such as the British & Commonwealth Military Badge Forum.
There are also some very helpful…"
"I am hoping someone can help me identify the rank or branch of military service that this man is from.
The sitter's name etc.This is a Sanger Shepherd 3 color transparency process from circa 1903-1905. I have no idea of the photographers…"