The attrition of 3rds in the 70’s was pretty high in the oilfield. This was mainly from the lack of motor training in all of the schools. The 80’s was a little better. The last batch of 3rds I worked with were very impressive. Highly motivated and were just a couple of months from their upgrade to Second and LTD Chief.
One spent some time on a Crowley Invader class tug as engineer so I assumed his 3rd covered as DDE. But after I thought about it, the Invaders are 10K hp but under 200GT. No license required.