US Signal, Practice Bomb, Mk 7 Mod 0
Practice bomb signal Mk 7 Mod 0 consists of a can of black powder fitted with inert fuze AN-Mk 247 Mod 0 and a blank .38-caliber cartridge which is used as a detonator. Signal Mk 7 is used with; practice bombs for observation of bombing accuracy.
The Mk 7 is generally the same as the Mk 6 except that the fuze is mounted off center in the Mk 6 and its black powder filling weighs about 1 pound more.
Collaborative Ordnance Data Repository