Trying to decipher this from marriage certificate

[bobb1960]

Trying to track down my grandfathers WWI service records - I note the following information from his marriage certificate (from 1915):

Under section 5 - Profession:

Driver
115th Co. [Company ?]
11th Division Train [Train seems to make no sense?]
A S.C
(farm labourer) [I guess this his previous occupation, pre conscription]

Can anyone shine any light on this information, what it means and where I should go to discover more detail?

Thanks in advance, Bob B