They were first introduced in 1935 and continued in production up until 1961. It was the Singer Manufacturing Company's finest domestic sewing machine.
The 201 came in four different sub-classes in the US
201-1 - a treadle operated version (much more common than hand cranks in the US)
201-2 - has an electric potted motor
201-3 - has an electric external belted motor
201-4 - uses a hand crank (more common in the UK)
The 201-3 has the usual sewing machine motor that takes a belt.