Alternator Main Circuit Breaker

[Joachim Gruber]

Finally got the "new to me" 260B into the air. The alternator was not charging. We noticed that the right most switch on the breaker panel was in the off position. It's a large switch with a finger guard forward of the switch lever.
My questions to the members are:
Is this the Alternator main circuit breaker?
or
Is it the Alternator field circuit breaker?

Does this switch trip like a circuit breaker when overloaded, or is it a switch that has to be moved manually to open?
Thanks in advance.