Badges of National Foundation Society a.k.a. Kenkokukai/建国会徽章

Kenkokukai/National Foundation Society (a.k.a. State Foundation Society, a.k.a. The Society to Build the Country) was an ultranationalist organization for "the creation of a genuine people's state based on unanimity between the people and the emperor".
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Source.

Another useful excerpt.

Source.

Membership Badge.

Reverse

建國會會員章 - National Foundation Society Membership Badge

 

National Foundation Day Badge.

1st variation.

Badge of identical design but has different color scheme.

建國祭之章 - National Foundation Day Badge

Formally it belongs to this group of badges https://asiamedals.info/threads/japan-national-foundation-day-badges-no.23155

 

2nd variation "white mirror and sword guard".

Size 40 x 25 mm.