Reverse
第4航空群 - Fleet Air Wing 4
Fleet Air Wing 4 (JMSDF) - Wikipedia
Original case.
海上自衛隊 - Maritime Self-Defense Force
第4航空群章 - 4th Fleet Air Wing Badge
These badges were manufactured by Nagawa workshop in Tokyo
Badges, watch fobs and plaquettes made by Nagawa Medal Works/名川徽章製作所
Founded in 1927 and still active today. Standard workshop labels.
asiamedals.info