Maine Central Wood Chip Car

I recently viewed photos from a fellow railfan's collection, from the 1970's, taken on former CP Rail branch lines in the Province of New Brunswick. Two photos from 1972, show a car used in wood chip service with the classic Maine Central ( Pine Tree Route ) logo, upon the left side of the car. The right side is lettered " Prime Mover for Maine Industry ".

I was able to focus on some of the car's details.........MEC 57101, Built 58, Cap 115,000 lbs ( although not clear ). The side doors appear to be hinged with a steel beam or bracing just above the door and running the length of the car, but below the top edge. It appears to me to be perhaps a reefer car that was modified for chip / sawdust service.

One of the views has a car being loaded at a sawmill in Nackawic, N.B., the other being the only car with a CP Rail RS-18 and van, in Fredericton, N.B.

Anyone familiar with this unique type of MEC car ?

According to "Northern New England Color Guide to Freight and Passenger Equipment" by Sweetland and Horsley copyright 1992,
MEC had converted 18 cars # 57000 - 57017 from 50' boxcars of the 9000 series to wood chip cars by removing the roof, raising the sides and ends by
2'10" and applying plywood doors. Maybe they added more numbers later on. The logo to the right of the doors is Prime Mover for Maine Industry. Ther were MEC green with yellow lettering. Cars were originally built in 1939 by Magor.