[Picture can be found here] (http://collectionscanada.gc.ca/pam_archives/index.php?fuseaction=genitem.displayEcopies&lang=eng&rec_nbr=3357544&rec_nbr_list=3357544,3231551,3241800&title=Sergeant+R.L.+Zengel%2C+V.C.+&ecopy=a006797-v8)
Sgt. Zengel's details can be found here
Myself and a fellow historian are not able to identify the meaning of the epaulette. It appears to be a number 12, yet Sgt. Zengel was a member of the 5th Canadian Battalion (Western Cavalry) CEF. Originally I thought it might harken back to the Battalion's history in the Northwest Rebellion or another iteration, but can't find anything.
Zengel was an acting platoon/troop leader at the time of his citation; 12 could designate his platoon number within the Battalion rather than the Company. Which would be wholly in line with how the Dominions designated their platoon-level units then and now. I'm not sure why it would be on his epaulette, as that is usually where one places their regimental, or perhaps Brigade unit number. It certainly does not reference the 12th (Canadian) Infantry Brigade; as the 5th Battalion was not a part of it (The West Cavalry had been unhorsed and designated an infantry well before the time of his citation, by the by).
So, for example, in the Canadian/British tradition; say a Battalion has, for argument's sake, 3 companies (in WWI this would not be the rule, but I digress) and sticking with the rule of 3s, 3 platoons per company. 2nd Platoon of the 2nd Company, would be, of course, referred to as such in the United States and most takes of the Continental system. However, in regards to the Britain and her Dominions, it would in fact be the 5th platoon of X Battalion. Platoons 1 through 3 belonging to 1st Company. TL;DR: Platoons were numbered consecutively at the Battalion level
A potential explanation.