On October 11, 1977, Belgium and Vietnam signed a Framework Agreement on Economic, Industrial and Technical Cooperation. Belgium had officially established diplomatic relations with Hanoi on March 22, 1973. As part of that agreement Belgium supplied diesel locomotives to 'help revamp Vietnam's Railways after years of destruction...'. The locomotives were funded by a state loan approved by the Belgian Parliament. It's interesting to note that the Belgian Embassy website says that the locomotives were delivered in 1978, while the builders plates on the locomotives say 1983. As it was a loan it was presumably paid back at some stage.

These 16 locomotives were built by Cockerill in Seraing, Belgium  in 1983 and are numbered 601-616. They were purchased using a Belgian Government loan. I guess Vietnam and China were at war at the time, so Vietnam's logical supplier was not 'available'. The initial order seems to have been made in 1978 but they were not delivered until 1983. The locomotives are used mainly in the north on heavy ('heavy' for Vietnam) freights.

Steam Locomotives generally used the traditional French classification system. A steam locomotive with a 2-8-2 wheel arrangement is classified as 141 class, a locomotive with  4-6-2 wheel arrangement is classified as 231 class etc. Pretty straight forward, except what they did  if  two classes had a 2-8-2 wheel arrangement I'm not sure. It didn't happen so wasn't a problem?