海軍協會 - Kaigun kyōkai/Navy League [association/society/organization]
"Naval institute" (translation that was popularized by one dealer) is simply incorrect.
Source.
Russian article Japanese Naval League (Kaigun Kyokai) (1917-1945) by Sofronov Timofey Yurievich.




Source.
Bulletin of Irkutsk State Technical University