Encryption devices are of great interest to me for several reasons. One reason is the importance of encryption in business, military, and personal security. This importance is, of course, growing with the proliferation of personal computing and communication devices. Another is that encryption is inherently a computationally intensive application perfectly suited for computers, my favorite subject. Also, my MS (from many many years ago) was in Mathematics, with a special interest in number theory—the basis of encryption. I have always tried to follow cryptographic developments, which have evolved significantly in my life. And, finally, encryption devices are technically "sweet": good engineering, technically complex, containing secrets, innovative, mixture of electronics and mechanicals, etc.
A short detour to products: My interest in this field led to us adding robust hardware security features to the x86 processors that my former company developed. Starting in 2003, all Centaur processors had extremely fast hardware-implemented random number generation, AES encryption and secure hashing algorithm (SHA).
Unfortunately, encryption devices are hard to find, and when you can find one they are very expensive, so the museum's collection is pitifully small. So, if you're interested in cryptography, there are many very good sites that have extensive collections on line such as here, here, and here. However, the one major device that we do have (the Fialka), is extremely interesting.