That was a good catch on the RCA number Johnno. I've done a search for the 24th(K) Fld Bde, RCA and found it has its origins in Fernie, B.C. This is in the East Kootenay district where the tunic was found. So maybe this explains the RCA number. Here's a brief history from wikipedia:
Following WWI the 107th (East Kootenay) Regiment was redesignated The Kootenay Regiment on 12 March 1920. On 15 December 1936 it was converted to artillery and redesignated the 24th (Kootenay) Field Brigade, RCA. It was redesignated the 24th Reserve (Kootenay) Field Brigade, RCA, on 7 November 1940; the 24th Reserve (Kootenay) Field Regiment, RCA, on 15 March 1943; the 24th Field Regiment, RCA, on 1 April 1946; the 24th Heavy Anti- Aircraft Regiment, RCA,
Maybe Thompson did enlist early as you say Clive but for some reason was rejected and when he re-enrolled was given his original number.
His service files consists of only five pages but it mentions nothing about an earlier enlistment attempt unless I missed something. Below are the remaining parts of the service file images that have not already been shown.
Would the Canadian Scottish have had a recruiting officer touring the province or do you think Thompson would have had to travel to Vancouver to enlist?