From 1912 any Territorial soldier who volunteered to serve in the Empire overseas was entitled to wear the Imperial Service tablet badge.
The original concept of the Territorial Force when it was founded in 1908 was that they should be mobilised for home service only.
It was only worn by Territorials and may often be the only clue to a man's battalion.
The soldier on the left probably was or had been in the 4th , 5th or 6th Territorial Battalion of the Norfolk Regiment.
Only seen on Territorial battalions of a regiment after 1912.