This is the standard version of the CX-52. It's a 6-wheel cipher machine of the 'pin-and-lug' type that is very difficult to break, even today. This is mainly because of the very high number of configurable options, such as the removable configurable wheels When the C-52 was introduced, it caused ripples throughout the cryptanalytic community [2]. Basically, the C-52 has 6 pin-wheels, chosen from a set of 12 different wheels. Each wheel has a different number of steps (and hence pins) to complete a full revolution, all of which are relative prime numbers in order to achieve the maximum possible cryptographic period. Registered Shipping