An updated original 2000 Series (Courtesy of Uraken.net)

A New 2000 Series on the Ikebukuro Line (Couretsy of Uraken.net)

Seibu 2000 Series

In Service: 1977 - Present
Top Speed:
105km/h (Service)
110km/h (Design)
Length: 20000 mm 
Width: 2849.5mm
Consist/Formation:
1 motorized car + 1 trailer cars (2 cars)
2 motorized cars + 2 trailer cars (4 cars)
4 motorized cars + 2 trailer cars (6 cars)
6 motorized cars + 2 trailer cars (8 cars)
Electric System: 1500v DC through overhead wires
Gauge: 1067mm (Narrow)

The 2000 Series is a four-door commuter-type electric multiple unit designed by Seibu for the Seibu Shinjuku Line.

The 2000 Series was the first train operated by Seibu to adopt a four-door body and also to get rid of the streamlined "Shonan Style" end cars. The new cab design features an emergency escape door on the front of each end car.

It was also the first train in Seibu's fleet to use regenerative braking, making it a much more energy efficient train.

In 1988, production of the 2000 Series was restarted. These trains are referred to as the New 2000 Series and have slightly different end cars with larger displays.

By the time the New 2000 Series was in full production, Seibu had replaced much of its fleet of older three-door trains with these newer four-door trains.