Hi Alex, Just going on the large size of the badge 93mm,
I think it's an Officer's undress Sabretache badge.
I have a 5th Royal Irish Lancers Officers undress Sabretache badge
in my collection which measures 115mm, and a 6th Inniskilling Dragoons one which measures 81mm.
please see link below to excellent reference website which shows pouch and Sabretache badges,
http://www.uniformology.com/HEAVY-CAV-03.html
best regards John