If you got that gun for less than $400, you should expect the police to be knocking on your door shortly after it arrives. You stole it.

All the 12ga/28" Miroku doubles I have personally seen have had approximately M/F chokes. Some of the early 70's guns are very tightly choked. Can't comment on the Miroku case colors because mine are all blued frames. Parker Repros out of the Olin Kodensha factory have very fragile case colors, but there was no real relationship between OK and Miroku. I mention that only because it is "Japanese case coloring."