The 2-6-0 is a Mount Savage built engine on the Pittsburgh & Western, a three foot gauge line that ran from Pittsburgh up into the Big Level region on the New York-Pa border. Purchaced by the B&O, the narrow gauge was gradually converted, the last of it in 1911.
The P&W locomotive roster is a can of worms, with engines constantly coming and going and re using numbers. The #4 was also used by a Pittsburgh built 4-4-0, and at east one other engine in between.
best regards, first posting,
long time lurker,
brian b