The type 200 was one of the first Belgian mainline diesel locomotives. It used the same engine as the earlier four-axle type 201, but with an increased output of 2,000 hp. Distinguishing features from its predecessor was the more angular body design and six axles. After the first order for 53, 40 more were ordered immediately. With a top speed of 120 km/h and a steam heating boiler, they were designed for mixed traffic. In the result, they could be found with all types of trains from freight to the TEE.

In 1971, 200.001 was rebuilt with a 4,000 hp engine and electric train heating. It was numbered 200.101, but rebuilt back in 1981. Also in 1971, the class was renamed to HLD 51. Since the 90s, they were mostly used in freight traffic. After the withdrawal of the last locomotives in 2003, some were preserved and some sold to foreign customers. So a two-digit number came to Italy, while two came to France.