The 12 stop cylinder on the early Richard's conversion was to serve the same purpose as pins between the nipples on the percussion revolvers, so you could safely carry all six chambers loaded. One of the main problems is the extra notches lined up with the thinnest part of the chambers. After a while they wound wear through wall of a chamber. The 12 stop cylinder was dropped from production in a short time and the 6 stop cylinder became the norm. I read that almost all the 12 stop cylinders that show use have one or more broken stops. Most of this information came from Dennis Addler's boook on cartridge conversions. The gun in the picture looks to be a nice one. Thanks for sharing.