See also https://asiamedals.info/threads/1933-kanto-large-air-defense-maneuvers-koishikawa-ward-air-defense-corps-participation-commemorative-badge.25039/
Size 34.5 x 30.5 mm.
Thickness 2.6 mm.
Obverse
關東防空大演習記念 - Kanto Large Air Defense Maneuvers
参加章 - Participation Badge
reverse...