The CO-OP brand of tractors was born out of a desire by farmers to reduce cost through collective ownership of machinery production. Early models were designed by Dent Parrett, formely of Parrett Tractor, and built in Michigan using a number of Chrysler components. In 1938, production moved to new facilities in Indiana. Cletrac also contributed a few models and some production occured in Saint Paul, Minnesota, at this time. After World War II, an arrangement with Cockshutt led to the new "E" series of CO-OP tractors which were simply re-branded Cockshutt models. Poor sales led to the CO-OP facilities being sold to Cockshutt in 1952, and the CO-OP brand was discontinued.
CO-OP history - article at Lancaster Farming