Pay close attention to what 67Dart273 has posted.
I'll try to clarify the terms that will make the discussion clearer.
Field is short for "electromagnetic field" The physical part that creates this is the rotor. The rotor gets electricity through carbon brushes the rub against slip rings on the rotor.
The pre-1970 'roundback' alternators have one brush grounded to the case and the other with a field terminal is in an insulated holder.
View attachment 1715584732
The only way to isolate the rotor from ground is to remove the grounded brush from the cast holder.
View attachment 1715584733
View attachment 1715584734
The 1970-71 'roundback' alternators had both brushes insulated from the housing. Each brush has a terminal. So these isolated field alternators have two field terminals.
View attachment 1715584731
In 1972 model year, a new 'squareback' alternator was introduced. It is also an isolated field alternator with two field terminals.
In the photos you posted I see a squareback.
I don't know what old and new refer to, but terminals used with insulated brushes do get insulated washers. Exception being if one is purposely reworked to be grounded so as to work with the pre-70 type of regulator and wiring.
There really shouldn't be a direct connection, but if there is, it should be protected (eg fusible link) and there should be a dash mounted voltmeter.
Insulating washers should be available locally, but if not this place has 'em.
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