Badge size varies between 18 and 20 mm.
"Early" badges.
1st variation.
Reverse
賛助員會章 - Supporting Member of Association Badge
財團法人 - Foundation
大日本防空協會 - Dainippon Air Defense Association
Hot enamel + light metal alloy.
Original case.
Size 55 x 45 mm.
Another example of 1st...
dainippon air defense association
dainippon air defense association badge
great japan air defense association
great japan air defense association badge
greater japan air defense association badge
japanese air defense association badge
japanese air defense badge
japanese air defense maneuvers badgesupportingmemberbadge
大日本防空協会
大日本防空協会徽章
賛助会員章