Well, the yellow text at the top tells you the ammunition lot for the complete loaded cartridge produced at Milan Arsenal. I’m not sure if they were just a loading plant or if they produced some of the parts as well.
Normally, one or more civilian companies produces the metal parts for explosive ammunition and ships them to a Government plant for the explosives to be loaded in. Some of them are “GOCO” operations, Government Owned, Contractor Operated plants, with some private corporation still running the place.
The markings on the lower edge of the cartridge case detail the nominal size and model of the cartridge case, 40mm M118, and the maker and their lot number, RNO-5-24. RNO was the Government code for Amron Corp. in Wisconsin. Last was the May, 1969 production date for the loaded cartridge case, not the complete round, which might have been assembled a month or more later. Hope that helps.