The Finnish State Railways (VR) ordered five units in 1959, but these were cancelled for political reasons. The units were offered to NSB for a reduced price. Three were designated Di 3b because they had a slight specification variation, with a (A1A)'(A1A)' wheel arrangement and higher top speed. Two units had come short enough in the production process that they could be given the same specifications as the other Di 3a units, but received a slightly longer body. The Di 3b were given the numbers 641–643. For part of 1960, no. 623 was leased by NOHAB and sent on a demonstration tour in Eastern Europe. This resulted in an order from the Hungarian State Railways, where it became the MAV M61. The Røros Line was upgraded and the Bergen Line units transferred to Trondheim in 1960, but increased need for hauling forced NSB to not use the units on the Røros Line until the delivery of the next batch of six units in 1965. The final delivery, of four units, was made in 1969.