A little mysterious, perhaps locally issued name tag.
Apparently Ikeda was an MG team leader. He was not even a squad leader, so he was not an officer. Usually even an NCO did not have a named tag; only officers had ones. I guess he was allowed an honor to have a named tag by platoon leader and made up an unofficial name tag.
弾二 is mysterious. In general most soldiers had a number in his squad. If it is that, it reads as 'the 2nd of ammo carriers in an MG team', that is, second man among carriers of ammo case. 2nd company was not usually an MG company so I guess he belonged to the MG company, say 4th company, and under heavy casualties he was trusted a HMG team. It is hard to read it as '2nd ammo section' because MG platoon seemed not so large.