Frangible glass grenades of various types were used by most of the armies involved in WWII. They typically were incendiary or smoke producing types. The Japanese used a variety of them, including this poison gas grenade. Frangible poison gas handgrenades were never widely used for obvious reasons. The only other that comes to mind is the French Bertrand Mle.1915 used during WWI.

There are two body styles in this size, a short and long neck. This is the latter. It is spherical and about 10cm in diameter (3.9"). There are no markings evident. Identified in the USN Japanese Explosive Ordnance (revised edition) Jan 1 1945 as:

"Prussic Acid, Glass, Type TB"

(Thanks Pete!)

AC (Hydrocyanic acid) is a clear liquid that vaporizes when released. It is a powerful nerve agent and in strong concentrations will kill instantly. Useful for clearing bunkers and other confined spaces.