I have a built up Model 12. It does have an add on rib. I have no idea whose rib this is. The rib extends all the way back to the back of the receiver. In trying to find out whose rib this is, a guy at a gun show said it was a "Peter's Rib". Anyone hear of this brand of rib. It is not a Simmons or Money Maker. I have seen this rib on other Model 12's, but it is not real common. Any ideas?