This MOW flatcar was built from the underframe of a GB&W passenger coach.

Flatcar X106 started life on the Green Bay & Western as 60' coach #106, purchased from Central Locomotive and Car Works (formerly Hicks Locomotive and Car Works) in July 1914 -- the final year that last passenger cars were built by the Chicago railroad car manufacturer.  The coach was put in maintenance-of-way service as X106 at an unknown date -- presumably soon after passenger service ended in the spring of 1949.  By the early 1970s the car was cut down to serve as a 60' flatcar.

The April 1973 Official Railway Equipment Register lists this car as "AAR car type M150."  I do not know what GBW X106 was typically used for, although cars of this type were commonly used for transporting rails, ties or ballast and for gathering scraps along the right of way.

The writing on the back of this black & white photo says:

Green Bay & Western RR
Flat car GBW X106
at Green Bay, Wis.  yellow car & trucks
9-5-71

The final disposition of flatcar GBW X106 is unknown.