I saw this on Gun Broker am thinking some kind of flare?
Seller description
Very good condition original, but unidentified WWII Japanese ordnance projectile. Measures about 40mm in diameter and 5 7/8” long. Has a rope pull type fuze, and is inert, safe and legal to own. Nice original paint and has two kanji character markings. Comes with original metal storage can that has original paint showing some flaking and a few dents. An interesting piece that warrants further research.
Seller description
Very good condition original, but unidentified WWII Japanese ordnance projectile. Measures about 40mm in diameter and 5 7/8” long. Has a rope pull type fuze, and is inert, safe and legal to own. Nice original paint and has two kanji character markings. Comes with original metal storage can that has original paint showing some flaking and a few dents. An interesting piece that warrants further research.