It's F&M coach 2 = SR&RL coach 21, built by Jackson & Sharp in April 1903 as the first half of an order of two cars. After the railroad shut down in 1935, the car body (sans trucks) was purchased from the scrappers by a local resident in Avon, ME and eventually found its way to Edaville after WWII.
The other car in the J&S order was F&M combine 3 = SR&RL combine 14, which is supposed to arrive at Sheepsot later this year.