Virtual Hagelin M-209

The M-209, designated CSP-1500 by the Navy (C-48 by the manufacturer) is a portable, mechanical cipher machine used by the US military primarily in World War II, though it remained in active use through the Korean War.
The M-209 was designed by Swedish cryptographer Boris Hagelin and manufactured by Smith & Corona in Syracuse (New York, USA). It was based on the C-38 which itself was an improvement of an earlier machine, the C-36.
This is a free online 3D simulation of the M-209 called Virtual Hagelin M-209 where you can learn how to use the machine to encipher and decipher secret messages and to find out about it's history.
m209.virtualcolossus.co.uk