I've owned two, a very nice sidelock 20, Model F that needed to be restocked to fit. The other probably very similar to the gun you're considering. As stated if it's tight, not beat or pitted you're just OK if a 12, good price for a 20. They usually have chopper lump barrels and occasionally decent wood.
Kawaguchiya was the first name used, then BC My Luck...and BC Miroku. All are good buys...especially the SxS sidelocks...Model F, Model FE and Model FE II.
Thanks for the correction. I temporarily forgot about Kawaguchiya. I think they wanted a name that would work in the States. Hence the name changes. If they'd stuck with Kawaguchiya, we'd probably be calling them "Kawas" today. Like Uggie for Ugartechea.
Kawaguchiya Firearms is the parent company...BC Miroku Manufacturing now does the firearms manufacturing. I think after the relationship with Browning was established they finalized the brand name under the BC Miroku label.