CMStP&P RR #3 was a former Catskill and Tannersville ng engine. The Milwaukee NG line that ran from Bellvue, IA on the Mississippi 30 miles west to Cascade, IA had two of the outside side frame 2-6-0's. John Tigges' book on the Milwaukee Road ng line, Iowa's Slim Princess, has some other views of this loco including this same picture. It WAS the Milwaukee's practice to ship the NG locos to the Marquette shops for major overhauls.
I worked with a gentleman who fired the Brooks moguls as a young man just before the Milwaukee sold the line to a local entrepeneur. He talked about how they would stop the engine on a trestle just outside of town that had a crosstie removed so the engine crew could get under the frame to access the oil fittings under the loco. He commented about how easy they were to fire after hand firing the larger SG engines. While on the extra board he used to jump at the chance to work the "narrer gage". Also there was a popular local beanery in Cascade that he was especially fond of.