If I ever get my next ship out of the UK, in it there is a Kawaguchia model "M' in it. Pretty similar to a 500 with a case colored action. No clue when shipments will  resume though. I have all the permits in place, hopefully by June or so. 
Steve, I had one of those--Miroku Model M, case colored, straight/splinter/DT/extractors.  Also as described previously by Mark and George.  Looked like a very basic Birmingham boxlock.  I know where it is, and sometimes think about seeing if I can own it again.  Doubt the current owner has used it much.  12ga, factory choked IC/IM.  Nice pheasant gun.
Had another one brought back by a Navy vet who'd been stationed in Japan.  That one was a 20, PG/splinter.  Pretty much like new.  Several years ago, Cabela's came across something like 10 of those, brand new.  I think they all stayed at the Sidney store.  Sold for around $1,000, IIRC.  The BSS are good guns, especially the Sporter.  But I thought those were nicer.  Lighter + double triggers, although they were extractor guns.
I bought a Western Field 20ga like that one years ago, but in nicer condition, as a raffle gun for our Ruffed Grouse Society banquet.  You won't see a lot of them made for Monkey Wards like that.  Must've been close to the time they got out of the gun business.