This type of wrist compass was built during the 50's and issued to the British troops. It was used during the Korea war and the Suez Canal expedition (1956). Its lack of precision lead the Military to use instead their classical hand-held marching compass (see Barker and Stanley). Moreover, its high radioactivity was the reason why it was no longer used.
This compass was also exported to a lot of countries. Export models only featured a serial number on the back with a "B"suffix, indicating Barker, like this one. Probably no radio-active material was used on these export compasses. Instead luminous (harmless) paint was used.