Reost 1947 SVRy

Actually that is not strictly true either. The 19 and 20 were designed as coal burners, but the S.V. ordered them with both straight and diamond stacks with the view of burning wood. They were also equiped with a master mechanic front end, per Floyd Carpenter. In actual practice the Sumpter Valley ran them on wood, wood and coal, or straight coal as conditions indicated. I have not seen or heard evidence that the Baldwins ever ran on straight coal so maybe the Alcos were not at their best on straight wood.
An interesting aside; the late John Bates, former S.V.Ry and O.L.C. brakeman, said that the when burning wood the firing characteristics of the 19 and 20 were exactly opposite. He related that one of them steamed best with a light fire, and the other had to be stuffed to the crown sheet. He did not remember which was which.