I’m reluctant to try reading foreign (to me) enlisted rank insignia from 100 years ago, but 3 chevrons (pointed down ... last time we had that in America was 1860s) suggests a sergeant of some sort.
It's the insignia of a British World War I Sergeant Major - today, that insignia is used for a Staff Sergeant (and Sergeant Major is an appointment given to certain Warrant Officers who wear a crown or the Royal Arms as rank insignia - although in Cavalry regiments a Staff Sergeant may still be referred to as Sergeant Major)