Does the writer mean "4H?" 4F is a Draft Board term for "Not fit for Military service." (For the youngsters who never experienced the Draft Board...)
I was labled 4F after my draft physical in 1971. Bad Eyes. That was a relief, because I had a really low draft number, 15 or some-such.
Of course, I got a medical waiver and enlisted in the Air Force in 1981, just to get a job and learn a skill. Worked, too. I worked in that field until I retired in 2012.