Hi Matt
In regard to your first photo, It was taken after outbreak of WW1 as the men do not have leather leggings which were replaced by cloth putties seen here on the men. The IY below the capbadge is easily explained - With a large increase in men joining the regiment supplies of the existing cap badge were soon exhausted and before new ones could be made, the old Berks Imperial Yeomanry capbadge (worn 1902-1908) was issued instead.
I recognise FG Ford, a Corporal shoeing smith in 3rd Troop B (Reading) Squadron of the Berks Yeomanry, and from memory lived in Upper Basildon. I would guess the chap on the right is also from the B Squadron. I will check our archive to see if I can spot his face.
I enclose another one of Frank Ford.
Should you or your relatives wish to visit our museum in Windsor to learn more about the Berks Yeo, please let me know.
Regards
AndrewFrench
(Asst Curator - Berks Yeomanry Museum)