[1] The Class featured the widespread Italian bogie, and the same Plancher compound engine of the Class 500, an arrangement in which the two high pressure (HP) and the two low pressure (LP) cylinders were paired together respectively on the left and the right side of the locomotive, with each pair being served by a single piston valve via crossed ports.

[10][8] The last two locomotives built, the 680.150 and 151, had been fitted experimentally with a superheater from the start, but results had not been positive, as the theoretical increase in performance was offset by the reduction of steaming ability.

[11][7][8] From 1918 to 1924, seventy-three locomotives were rebuilt with a new small-tube superheater; initially allocated to the subclass 680.2XX, they were eventually reclassified in the new Class 681.

[16][17][18] The unrebuilt locomotives continued to serve on secondary roles for the rest of their careers; before World War Two they were already being used sporadically, but during the conflict they were returned to active service.

[19][7][18] One Class 680, the 680.037, survived in preservation; after a lengthy stay in Merano, she was eventually transferred to the Pietrarsa railway museum.