LLT has 4 brigades arriving in France on 1 Oct 1915 - the 1st, 2nd, 3rd and 4th West Lancashire Brigades RFA which became 275, 276, 277 and 278 Brigades RFA, all formed in 1908.
A west Lancashire connection would possibly put him in one of these but that would be about as far as one could go without his service record.
maxD
And his number denotes a 3rd West Lancs RFA man
675001 – 680000: 285 Brigade, RFA/ 2/1 West Lancashire
680001 – 685000: 276 Brigade, RFA/ 1/2 West Lancashire
680001 – 685000: 286 Brigade, RFA/ 2/2 West Lancashire
685001 – 690000: 277 Brigade, RFA/ 1/3 West Lancashire
685001 – 690000: 287 Brigade, RFA/ 2/3 West Lancashire (BROKEN UP FEB 17)
690001 – 695000: 278 Brigade, RFA/ 1/4 West Lancashire (BROKEN UP OCT 16)
690001 – 695000: 288 Brigade, RFA/ 2/4 West Lancashire
see
http://www.longlongtrail.co.uk/soldiers/a-soldiers-life-1914-1918/renumbering-of-the-territorial-force-in-1917/renumbering-of-the-tf-artillery-in-1917/Lots of pointers toward the man in the Medal Card being the man in the photo but still needs a clincher I'd say.
Just to cover the point can you confirm there is definitely no number on his marriage cert. Also, are there any children during wartime/shortly after? Their birth certs may have a number.