The B&O M-56 cars were built in May ‘52 with 10-panel sides, 8’ 3/5/5 Youngstown doors (counting corrugations). They had diagonal panel roofs and Duryea underframes, Champion-Peacock handbrakes and US Gypsum running boards. 
—
Randy Hammill
Prototype Junction
http://prototypejunction.com

Modeling the New Haven Railroad 1946-1954
http://newbritainstation.com