The service records of Captain George William HALL have been digitized and are available online
http://central.bac-lac.gc.ca/.item/?...&id=B3942-S036 .
A quick look at his file shows that his original unit was the 109th Battalion, however for a short time he was attached to the 125th Battalion and afterward spent a significant portion of his overseas service "seconded" to the Royal Engineers Railway Operating Division or in other (non-regimental) duties. He was Mentioned in Despatches. He likely kept his 109th badges during his time on the General List and during secondment - entirely appropriate. At the time he had his photograph taken he was probably working with the RE/railway troops and identified himself as such to the photographer who so listed him. Capt Hall listed his previous civilian occupation as the proprietor of a machine shop and garage and likely was useful in keeping the rolling stock rolling.