Bomber Crew Uniforms

Hello!

I am looking at the uniforms of the early bomber crews, particularly the RCAF who were flying with the RAF (1941). In particular, I am looking at serial numbers that were inside the uniforms– and have one which I wish to know more information about (if possible!). THe serial/size/? is SMZU 26 — not sure if it is a smudged size or mis-recorded — the serial was taken down in 1941 following an air accident.

Any help would be most appreciated!