A search for the word rotor on SE Crypto brings up fifty questions. Most of them are about the Enigma, of course, but some are about the Bomba and Bombe, and one is about the Fialka (a Russian electro-mechanical encryption machine). Contributions about the SIGABA (4) and the M-209 (4) do not come up because they are poorly tagged, some as
classical-cipher. All of the devices mentioned thus far have rotors, the Bomba and Bombe being different from the encryption devices.
Given the importance of rotor-based encryption machines in the history of cryptography (both mechanical and electro-mechanical devices), why don't we create a tag that covers them? The tag of
rotor-based-encryption will include general questions about the math, theory, and practice of rotor-based encryption and help unify it as a topic on this website. See this question that is in need of proper tagging.
For details about rotor machines, please see this website.
Now, if we were to be precise, we would make a distinction between rotor-based machines and pinwheel-based machines, but do we need to do that? Why not put them together under
rotor-based-encryption? Perhaps we could create a tag synonym named
pinwheel-machines and explain our rationale in the usage guidance.