Mills redesigned the grenade to make it safer and more efficient and decided to manufacture it by casting, By 1916 the Mills No.5 Mk 1 hand grenade was in wide scale production by many British contractors, including the Mills Manufacturing Company in Birmingham.
During the course of WWI, some 75 million Mills grenades were manufactured in various Marks, William Mills was knighted for his services in 1922.
An improved variant of his grenade, the No. 36M Mk1, remained in service as the standard British hand grenade until 1972.
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