See https://asiamedals.info/threads/tajimi-city-friends-of-the-navy-association-badge.25400/ and https://asiamedals.info/threads/friends-of-the-navy-association-badge.26344/
Reverse reads
海友會, where
海 - Navy
友 - Friends
會 - Association
On the right
一 宮 - Ichinomiya...