but 1960 to 1977 is when I had my 'papers' active. My 'normal' waters were the Puget Sound to South West Alaska. Don't know about/when the change came on required service time but it was a full 365 days at that point. Haven't looked at the regs. for years so they may have put in different 'grades' for lic. requirements some time in the past.
The way I was able to log so much time from age 16 to 18 or 19 was working with Sea Explorers and with my neighbor who was a Captain of a Foss Tug. Lots of tows were at three knots against the current so almost always had a salmon rig hanging over the side. Actually caught a fair number of fish ... "cookie" and the crew, ate fairly well. But then again, you worked your butt off.
My ticket covered hulls up to 150 tons as the Master and 350 tons as the second. Rarily ever got on something even on the 150 ton side and my only 'rides' for larger hulls had the US Navy or USCG painted on the side.
And these guys weren't about to turn their toys over to a young buck like me.
Trust is one thing ... stupidity is another.