This is generally referred to as the hook type and is the predecessor to the N-1 deck jacket.
It was adopted in the second half of 1943 and was first distributed in 1944, which represents the war period.
A generation ago this jacket had a front zipper, but due to frequent malfunctions from salt damage it was replaced with a ratchet clip.

・Exterior: cotton cord fabric
・Lining: melton wool
・Interlining: rayon
・Rib: wool rib
・Front zipper: ratchet clip type
・Sewing thread: Catania thread (cotton thread)

Made in Japan