The details you provided point directly to a rare, highly collectible piece of vintage automotive inventory: a New Old Stock (NOS) Radiator Fan Shroud Accessory explicitly manufactured for 1937-1940 Chevrolet/GMC 1/2-Ton to 1-Ton light and medium-duty trucks, carrying the historical GM Group number #1.285 and GM Factory Part Number 365402.Understanding the Part SpecificationsClassification: Genuine GM Factory Approved Accessory (Group #1.285 typically indexes cooling system accessories, brackets, or shrouds in early Chevrolet parts catalogs).Part Number: 365402.Vehicle Compatibility: Fits 1937, 1938, 1939, and 1940 Chevrolet and GMC trucks ranging from 1/2-ton pickups to 1-ton commercial chassis.Value for Collectors & RestorersFinding this component in NOS (New Old Stock) conditionmeaning it is an original assembly-line or dealership-network part that was never installed, used, or subjected to engine wearis exceptionally rare for pre-WWII trucks.Cooling Efficiency: In original configurations, these shrouds are highly sought after to maximize airflow from the mechanical fan pulling through the radiator core. This corrects the common over-heating issues seen when idling modern fuels in vintage engines.Authenticity: For judges at vintage truck meets, having a stamped GM accessory part with its original packaging, box, or factory stampings exponentially raises a vehicle's build pedigree compared to modern aftermarket aluminum alternatives.