Thanks to everyone for you help (somewhat confusing), so far. Firstly 'Jack' suffered with chronic breathing problem during his life, so he did survive the gassing. I have his short birth cert, that shows his d.o.b. as 1897. Jack did die in Staffordshire on 15 Apr 1961, but there was no will as his wife Nellie had to go through probate at Birmingham, in june 1961, to inherit his estate of £12,516.
I have previously looked at the Field Artillery record for Albert John DAVIS, but that is the wrong one, as the next if kin indicates a mother (of the wrong name) and his was deceased. The information about him joining the Canadian Regiment No. 175 in 1914 is useful, but although he moved to the Birmingham area when very young, he was born in Gloucestershire. The information about Albert DAVIS and Frances Catherine KINGSFORD being his parents are correct. I'll check out the possible attestation paper thanks.