Who manufactures the M67 grenade?

Answer 1

The M67 has been manufactured by at least three distinct companies, each of whom utilize unique markings to distinguish their product.

"JA" marked M67s were manufactured by the Joliet Army Ammunition Plant, located just south of Joliet, Illinois. Production of the JA M67 took place at the Kankakee facility of the JAAP (previously known as the Kankakee Ordnance Works) during the Vietnam War, ending sometime in the late 1970s. The JAAP no longer manufactures live-ordnance.

"LS" M67s were manufactured by the Lone Star Ordnance Plant of Texarkana, Texas, a contractor-operated facility previously run by the Goodrich Corporation (former B.F. Goodrich Rubber Corporation) under the auspices of a defense contract. LS M67s were produced throughout the Vietnam War and, perhaps, well after; however, the LSOP has since been deactivated (as of 2009) courtesy of the 2005 BRAC (Base Realignment and Closure) issued by the United States Department of Defense.

"MA" M67s were/are manufactured by the Milan Army Ammunition Plants (composed of what was, originally, the Milan Ordnance Depot and Wolf Creek Ordnance Plant), located adjacent to Milan, Tennessee. The MLAAP is a member of the United States Army Materiel Command (AMC), whose purpose is the assembly, packaging and storage of conventional ammunition exclusively for military use and, as such, is the sole former-manufacturer of the M67 still in business today.

It's probable that other groups have also created the M67 over its service lifespan, however, I've no records to indicate such.