The NS 3500 was a series of express train steam locomotives of Nederlandse Spoorwegen (NS) and its predecessors Noord-Brabantsch-Deutsche Spoorweg-Maatschappij (NBDS) and Maatschappij tot Exploitatie van Staatsspoorwegen (SS).

The locomotives fully met the expectations: to transport heavy trains above the normal weight on time.

After all, the post had to be in Berlin on time and the connection to the mail boat had to be made in Vlissingen.

[1] The colour of the locomotives was dark blue, trimmed with black tires and red piping.

The tender and the lower part of the cab were given an extra embellishment, consisting of a wide white stripe outside the red one.

According to the manufacturer's custom, the wheel arches were trimmed with double brass edges, between which the name Beyer-Peacock.

The NBDS ordered these locomotives for the mail trains from Vlissingen via its own line between Boxtel and Wesel to Oberhausen and Haltern in competition with the SS.