RR,
The MCR2 was used from 1949 with the E3L generator.
Swinging arm models used the RB 107 until 1957 and then the RB108.
37097 is a common regulator for the E3L.
I am not sure whether the plunger models continued with the MCR2 after 1953.
The later MCR2 regulators had an identical mechanism to the RB107.
Trev.