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


Above: Photos © Patrick.
All three body-forms on a row.

Right : Photo © Justin. Typical remains after detonation.

Photo left © B.F van Rossum , right photo © B. Prévot.

More relic-pictures on M15's :