For once I can help, rather than just learning from you guys.

I have just bought a Miroku 12 bore side-by-side with 28" barrels bored modified and full choke. Whilst browsing through the list of boxlock ejectors in Holts Sealed Bid sale about six months ago I spotted two of these for sale. having never heard of this model I researched it and found a rave review in the 1975 American Guns Review annual, where it was listed as the Browning SBS.
The Holts estimates were about £300 / $400 plus their 30% fees and carriage, so I left a bid on one, sight unseen. I failed; it went for £382, or £500 all in, too much for me. So I had a look at the British Gun Trader website and found half a dozen for sale. One in the middle of Wales looked good in the photos, so I bought it for £275 plus £100 for transport to me here in the south. It is fine and tight, almost like new, although the bluing on the barrels is a bit thin. It shoots well. This may become my low-cost gun for steel shot if and when the law here changes.

My research seems to show that they were all made between 1974 and 1977, and were slightly cheaper than the Miroku over and unders of the time. My serial number is 452xxx, and all the others offered for sale here are also 45xxxx. I believe a batch of about 3,000 were imported here. Mine is proofed by the Birmingham Proof House for 1976. The barrels are beautifully made with chopperlumps. The stock is fixed to the action with a stock bolt, and mine is absolutely straight, with no cast at all, which is a bit of a problem for me. It features a 1970s white line spacer, which is quite quaint.
The barrels are clearly stamped "Made in Japan and Assembled in Korea", which I suppose kept the cost down a bit. I have a copy of the original 16 page booklet which shows that they made either single trigger or double triggers versions, and also three different forends, a splinter for England, a middling version and a big beavertail. these relate to model numbers 150, 160 and 170 respectively.

The handbook also list the system of choke markings with one * or + meaning Full Choke, up to *** or SS for Skeet. The safety catch is automatic, for a field gun.

If you have any other questions let me know.

HB