1918: Grave lists him as "Shoeing Smith"
1919: Three listings on the medal roll; one as "Shoeing Smith", the other two as "Driver". EDIT: a driver in this case is someone who rides horses that pull heavy artillery guns, I believe they are in teams of horses if the gun is very heavy. He died in the Battle Of The Selle, and I'm not sure if Shoeing Smiths actually participated in the battle. He died of wounds.
Enlisted in 1909.
For research purposes, etc:
835979 Driver/Shoeing Smith Frank Carroll
307th Brigade, 61st (2nd South Midland) Division, XVII Corps, Third Army.
EDIT: Supporting evidence that he was, in fact, a driver in the RFA, as 307th Brigade of 61st Division was not part of the Royal Horse Artillery, but the Royal Field Artillery. Source: http://somme-roll-of-honour.com/Units/british/61st_Division.htm
This is an interesting one and it seems that Shoeing Smith is a rank distinct to some cavalry units including the Royal Horse Artillery and is now represented by the role of Farrier, but was also in use in the Royal Field Artillery presumably because of the heavy reliance on horses for transport. It may be that he re-roled to driver if his unit received motor vehicles - a sort of natural step for someone looking after the unit's transport!