The AN-M30A1 was a World War Two era general purpose (GP) 100-pound bomb that entered service in 1942. The AN-M30A1 was a slightly modified AN-M30 US Army developed bomb, differing in the base plug/plate construction, and the use of a different adapter-booster. The bomb served the US for about 20 years.
From the Bulletpicker website
These bombs are all general purpose high explosive bombs.
To overcome the erratic flight of these bombs when dropped from high altitudes by very heavy bombers, the tail assembly of the 260 pound Fragmentation Bomb M81 replaces the customary tail unit, which is two inches shorter, for such missions. Use of the Cluster Adapter M22 permits single suspension for four GP Bombs AN-M30 or AN-M30A1.