Perhaps one of the strongest pieces of evidence that it is indeed Alonzo James Brackett is what reynolds12 pointed out
, that Alonzo served in WWI and therefore could have earned the War & Victory medals which the soldier in the photo is wearing the ribbon pin of. There couldn't have been that many Gunner A. J. Bracketts in the R.C.A. with the same embarkation date who also served in WWI.
In actuality, if you check the LAC, there is only one A. Brackett that served Canada in WWI, and it's Alonzo.
So, logically, we know the man in the photo served in WWI because of the medal ribbon pin he's wearing and if the man in the photo is one Gunner A. J. Brackett then it must be Alonzo James Brackett because he's the only A. Brackett that served Canada in WWI -- unless the LAC is missing a record or if the original article identifying that man as A. J. Brackett is wrong.
LAC WWI Results Personnel Surname: Brackett
https://www.bac-lac.gc.ca/eng/discover/ ... h=brackett