- He was on a job.
- So was Salazar. He was in the six-four.
- Huh. And then you went over to the D.A.'s.
- I was retired on a medical.
So you were wounded in action?
what does "three-quatered" mean on this context?
I bet it means "evaluated to have a 75% disability."
Following WWII (I don't know about other wars), American soldiers wounded in battle were medically evaluated to determine the extent to which they were disabled.
Disability ratings determined the size of one's monthly disability check, as well as numerous other benefits (the percent of interest rate relief for home mortgages, the size of tuition rebates for college courses under the GI Bill, etc.)
According to my mother, her uncle spent the rest of his life crabbing about the fact that he had been given only a 10% disability.
So even though the speakers quoted in the passage are obviously not Americans, I bet that being "retired on a medical" and being "three-quartered" means that some Board has evaluated the person as being 3/4 medically disabled -- a 75% disability rating.