There were 2:
One of my favorite books: Norfolk & Western Steam (The Last 25 Years) by Ron Rosenberg, says of the M2 Automatic:
“In 1947, the N&W faced the reality that most of the locos in use as switchers were no longer economical to operate. Two M2 4-8-0’s were modernized in an attempt to create a steam switcher with the high availability and low maintenance demands of diesels, but with lower initial cost. The 1100 and 1112 received automatic boiler pressure controls and safety and standby devices to minimize the need for human attendance. Hennesey lubricators were fitted to the drivers, and each received a tender holding two days’ supply of coal and enough water for eight hours running. A longer combustion chamber, over-fire air jets, a low-speed stoker, and a turbine-driven draft fan were among the changes made to increase thermal efficiency. The locos worked as expected, but the availability of ex-C&O 0-8-0’s in 1950 made further experimentation point-less.”
So they predated the S1’s:
and the possibly more famous S1a’s:
Number 244 being most famous of course because it was the last loco turned out by Roanoke Shops.
