Hi Noreen
That is indeed his Canadian Army Regimental Number.
The Letter shows his geographical Military District and the number is with a block assigned to the sub-unit that he at least initially attested to. It had no bearing on subsequent types of Army service. In this case, B equals Military District 2 (Eastern Ontario) and the number falls with in that assigned to No. 2 District Depot, Royal Canadian Army Service Corps or RCASC. Was he a tradesman?
You can write for his service file here:
http://www.bac-lac.gc.ca/eng/transpa...iles.aspx#tab3
If you are
not his closest surviving relative or
cannot provide proof that he has been dead more that 20 years (pic of headstone, Obituary, Certificate of Death etc) then you will get a file that his
heavily censored for personal info and I would guess you don't want that.
Send the proof with your request and specifically ask for an un-redacted file.
regards
Darrell