HR6561 FS, 3-units pack refrigerated wagons Hgb 2-axles (2 without brakeman's cab, 1 with), white, red stripe, UK loading gauge, ep. III

In 1931 the FS started the construction of a large group of refrigeration wagons type Hgb specialized for the transport of perishable foodstuffs to Great Britain, derived from the typical Italian "sloping roof" refrigerating wagons already known throughout Europe at the time.

These wagons, built in 700 units, of which 550 equipped with a brakeman's cab, having to respect the English gauge for circulation on the British lines and for the ferry across the Channel, were visibly smaller than the corresponding "European" gauge wagons. while maintaining the same length, and were equipped with the vacuum brake devices and the long handbrake rods on the sides, mandatory requirements in Great Britain.

In addition, the English-shaped refrigerated wagons were also easily recognizable by their livery, as there was a visible red band on the sides and the large logo with the anchor to indicate the possibility of ferry.

Between 1932 and 1945 these wagons were hired to the Ferry Boats Company for England - Milan, and then returned directly to the FS. In 1946 a new series of 600 Hgb wagons was built, all without a sentry box, with some improvements such as roller bushings; finally in 1947 a further series of 300 Hgb wagons was built with a metal case, with a visibly different appearance from the previous ones but maintaining the same general shapes.