What did a temporary petty officer rank mean?

What did the temporary part of a World War II petty officer rank mean?

It generally indicates an acting or wartime-service appointment rather than a commissioned rank; a merchant-service background could make such an appointment plausible.

A temporary appointment differed from a commissioned rank. It could mark acting status, service limited to the war, or the return of a reservist whose experience was immediately useful. The questioner's merchant-marine background fits the Navy's need to employ experienced seamen as wartime petty officers. This remains a cautious interpretation of one service record rather than a universal rule for every temporary appointment.