This information was found on a website which explains the army numbers.
http://armyservicenumbers.blogspot.co.uk/p/number-prefixes.html
SS – Army Service Corps. Supply Special (butchers, bakers, clerks etc)
Army Service Corps. Supply Branch
S1, 2, 3, 4 - Army Service Corps. 1st/2nd/3rd/4th New Armies Supply (S4 Labour)
My mans number was Regimental No S4/407418, this seems to indicate he was in Special Reserves.
The number SS was Supply Special. As he didn`t have this prefix even though he was a baker, does this indicate that he didn`t actually do any breadmaking while in Russia.
If not, what would he have done.