I worked for ECO in 1995, my seatime letter said 12 hour days and I received that credit.
This was aboard a Submarine Support Vessel, which is a fancy name for R/V. At the time the ship had 3 ABs and the captain worked 2 in the daytime and 1 at night. And it was work, we were not even allowed in the wheelhouse. No overtime, it’s not in ECOs vocabulary.
Mates did 4 and 8 in the wheelhouse and then 4 hours on deck on their own schedule.
Slightly better conditions that a certain west coast ship where there was a timeclock in the chief mate’s office. You were required to clock out for all your meals and breaks, when you accrued 12 hours you could knock off. I believe that the Department of Labor put a stop to the practice.