The M15 was a WP bursting smoke grenade. The body was made of steel and the fuze carried a detonating fuze to shatter the body to pieces to free the WP filling.A dense white cloud was the result. The white phosphor also had an incendiary effect. Grey painted body with yellow markings. At least 3 different body forms are known. Between July 1943 and December 1945 there were 5.828.739 grenades were produced.
Description copied from FM 23-30-1944 :
This grenade is generally similar in size and shape to the irritant gas hand grenade CN-DM M6, but has rounded corners. It is equipped with the M6A3 detonating fuze with 4½-second delay. This grenade is different from the other chemical grenades in that it is a bursting type grenade. On exploding, the solid pieces of WP will be scattered over an area about 25 yards in diameter and will burn for approximately 30 seconds.
Total length : 136mm Length body : 114mm Diameter : 64mm Weight : 880gram Filling : 425gram White Phosphor