NEC Table 210.21(B)(3)
I look at the above NEC Table and I find a strange inconsistency. For a circuit rating of 20A the receptacle ratings can be either 15 or 20A. Now if you look at the circuit rating of 40A the receptacle rating is either 40 or 50A. The inconsistency is that in the first case a receptacle rating of less than the circuit rating is allowed. In the second case a receptacle rating that is greater than the circuit rating is allowed. Now which case is more correct? I would say the second case. I know that this NEC Table applies to two or more receptacles on the same circuit but one can not overlook the possibility of a receptacle getting burned. If you were to plug a 20A load to a 15A receptacle protected by a 20A OCPD then you're going to have a problem.
Eric Kench, P.E.
If it's not broken don't fix it