Im looking for some ammo Guru's to help me figure out what this is. I found it on a rocky beach in South Korea this afternoon. Its badly corroded..in fact i cant tell you how long the case is because the end has been either broken or eroded. The only markings i can see on the end are the numbers "4 5" on the bottom and either "S I" or "S J" on the top...its really hard to tell. I was kinda hoping it was korean war era but who knows it could be modern.
here are some poor pics (penny for scale)
here are some poor pics (penny for scale)

