This is a design for a 4,000 pound GP bomb of the same general construction as others in this class.
Filling: Tritonal (2002 lb, 910 kg) or TNT (1856.8 lb, 844 kg) with a larger booster, the T21, which is like the M115 except for its increased size.
OP 1664, Volume 2 - US Explosive Ordnance (1947)