Got this the other day there is not much left on the base but from what I have seen and sourced all indications point to it being a 37mm x 155mm Japanese cannon shell.
The cases I saw on the web had the F also what looks like 2 small flags is whats left on a better example of a pair of either cannons or flags and I got it pretty cheap.
Have not got much IJA stuff at all for that matter couple of Arisaka rounds a Shin Gunto 98 and this one.
Thoughts!