Kelly,
Good catch. I believe this photo was taken before 1900. It has the old boiler. By 1909 it had a new cylinder saddle but retained it's 4 bar crosshead.By 1909 a long smoke box and straight stack had been installed but it still had the old boiler. It got a new boiler in the 1913-15 era. It seems to have received an "alligator" style crosshead and forged end rods when it got the new boiler. It retained the box headlight after the boiler change but it was electrified instead of kerosene burning.
Colorado has now approved the retention of the "National historic register" status if the engine is moved. As soon as the "feds" sign off we will move the engine to the C&TS so restoration can begin.
Our plan is to restore it to the earliest time frame consistent with the new boiler. That will place it 10 to 12 years before the K-36s were built.
We have a picture of it doubleheaded with a slidevalve K-27 departing Chama with a passenger special. While the date is not clear we believe that picture was taken between 1915 and 1920.
We are actively encouraging donations so this exciting project can move forward.
John Bush