The M300 was built by American Car & Foundry in 1935, Order #1432, as Seaboard Air Line RR 2026, part of a three car order, 2024 thru 2026. She was sold to the Aberdeen & Rockfish as 106. In 1951 and was purchased as Salt Lake Garfield & Western M.C.3 to replace their electric cars. Finally, in 1963 she became part of the CWR roster where she was numbered M300. So (in 2019) she’s 84 and still rolling along. Not bad eh?
Daughter Annalise, who works at Berkeley University and has access to their archives, found these pics for me: