Of the two, I would start with the Gunner (Royal Artillery). He would be more likely to come from a moneyed family than someone serving in the Army Service Corps (ASC). I hasten to add I am making a huge assumption there, which is not to denigrate anyone who served in the ASC. Its just that the RA attracted officers from a broad range of backgrounds, whereas the ASC in general attracted those from a less privileged background.
If your man came from Cornwall it would be helpful in tracking him down. Neither of the two chaps above may end up being correct, given what little you have to go on right now.
My understanding is that Edwinson Green made very few U/Os and that a pair would be super-rare.
Tim
