I was reading [How general is the Lagrangian quantization approach to field theory?](http://physics.stackexchange.com/q/3500http://physics.stackexchange.com/a/3501/50770) where it is mentioned that some quantum theories can have no classical limit or even more than one classical limit. 

One possible example might be quantum spin, which doesn't have a classical analog. What is the precise condition that determines the number of classical limits of a quantum system? Does the condition arise solely on imposing $\hbar \to 0$, which I am not able to see for quantum spin? 

What are some other examples of this, especially of systems having more than one classical limit?