The S-3 Canadian Small Arms School occupied the former Long Branch Aerodome for small arms training during WWII.
From:
http://militarybruce.com/abandoned-canadian-military-bases/abandoned-bases/ontario/
"In January 1917, the newly designated Royal Flying Corps, Canada, the forerunner to the Royal Canadian Air Force, opened the RFC Training Centre at Long Branch. The Long Branch training centre also provided instruction on flying boats at nearby Hanlan’s Point in Toronto Harbour, the first seaplane base in Canada.
By July 1917, the flight school re-located to the Armour Heights Aerodrome. Long Branch became the Cadet Ground Training School for the Royal Flying Corps. Both the school and the aerodrome closed in 1919.
Not the slightest trace remains of the aerodrome today.
In June 1940, Small Arms Limited, a crown corporation, was founded under orders of the Ordnance Branch of the Department of National Defence, who authorized the construction of the factory for production of small arms rifles. The factory was built on the east end of the former Long Branch Aerodrome property. The factory produced British-pattern small arms such as the Lee-Enfield and Sten sub machine-gun.
In October 1940, No. 21 Non-Permanent Active Militia Training Centre was established, remaining until March 1941, when A-25 Canadian Small Arms Training Centre (Eastern Canada) was formed in its place. The Army camp served not only as a training centre for soldiers, but as a proving establishment for firearms manufactured by Small Arms Limited.
Small Arms Limited was shut down in December 1945 and production was taken over by Canadian Arsenals Limited, with the facility being re-designated as the Small Arms Division of C.A.L.
The name of the camp was changed to S-3 Canadian Small Arms Training Centre (Eastern Canada) in November 1942 until closing in October 1945. The 2nd Infantry Training Battalion took over the camp until closing in May 1946. The firing ranges remained in use by the militia units in the Toronto area, along with the RCN, RCAF, RCMP, OPP and the range’s original occupant, the Ontario Rifle Association."
And being the camp RSM with DCM on the end of his name, I think his brass polishing days were well over