I have the Madis Model 12 book also & on page 53 he states "Winchester's solid ribs were usually made as a part of the barrel, a milling job that required a great deal of time by expert machinists." Note the word "usually".
I've often wondered about that statement because of the cost of machining & finishing such a complex rib & barrel assembly as compared to what Winchester charged.
To use 1953 for example the retail cost of a standard plain bbl Model 12 was $93.85 & the cost of a standard gun with the solid rib (matted rib as described by Winchester) was $110.35. That is a 17.5% increase in price which is significant but still less what I would think the complexity of the job would add.
Also I just got done looking at the muzzle of a 12 ga solid rib model 12 produced in 1953 using a magnifying glass & while it is an excellent job, you can absolutely tell that on this particular gun the barrel & rib are two separate pieces but I cannot see any solder at the join line looking directly at the muzzle so I've no idea what type of solder was used by looking at it.
I'm sure someone out there has put solid rib Model 12 barrels into a hot bluing tank & if they were put together with soft solder it would be common for the ribs to come off so I'm going to make the assumption that Winchester may have used a silver solder process to attach ribs & possibly there are some solid ribs out there that were made as Madis described but I do know that the one I'm looking at wasn't.
