What Winchester would actually do a lot of times is send a Model 12 to Simmons with or without a solid rib. No proof mark shows it left as a field grade and if it only has a proofmark on the barrel, it left as a solid rib. Simmons would remove the solid rib and replace it with a vented rib and/or they would put a vented rib on the field guns. When it was sent back to Winchester, if there were no Simmons trademark on the rib, it was either installed by Simmons and returned in the white, or it was installed by Winchester. This is why collectors only collect the ones without a name on the rib, because they were actual Winchesters. But Simmons did buy Model 12s, put their ribs on and sell them theirselves. This is all pretty common knowledge to Model 12 collectors.
