Re: D&RGW mikes

Some K-27s were retired with slide valves and Stephenson gear. I have seen some discussion that there might have been a limited number of early conversions that ran with piston valves and Stephenson gear for a short time. The earlier conversions with "inboard" piston valves may have reflected the intention of using Stephenson gear, the Walschaert required extra parts to transfer the motion between the gear and the piston valve.
The change to an "outboard" piston design places the valve gear motion and piston valve in the same plane, reducing maintenance costs. The same offset to the outboard position was used by engines with slide valves using Walschaert for the same reason.