This one is defintely unofficial
The postcard is by Fred Spurgin ( Izydor Spurgin ) , many of his wartime comic postcards were a reflection of contemporary attitudes and tastes. There were cards on patriotism, politics, women at work, comments on government policy.
This one may be connected to either compulsory military service, which was introduced in 1916 or perhaps a change in policy about "private" badges.
"These private “On Service Badges” were made illegal on August 4 1915 and any companies that had been allowed to issue their own badges were instructed to withdraw them and issue official badges instead."