A 6'2" left-hander signed as an 18-year-old by the Orioles, he was left unprotected in the "first-year" portion of the Rule V draft, and the Reds snagged him. Apparently, that got you on the 40-man roster, and he went to camp with the Reds, even though Henderson was ticketed for A-ball.
Here's a Topps picture, my attempt to color-correct it, and a black-&-white of Henderson with Chet Nichols:
At the end of 1964 (Henderson went 11-6 and 3.14 for Peninsula) the Houston Colt .45s (in one of their final pre-Astros acts) took Henderson in the regular Rule V draft, so there are probably some pictures of him in Astros gear from 1965 Spring Training, but I haven't found them.
He didn't make the Astros (obviously), was returned to the Reds, and spent the next three years pitching with middling success for Knoxville in the Southern League (AA).
At the end of 1967, he was promoted to Buffalo (AAA) and went 2-3, 2.48 in his five starts there. A nice AAA debut…and yet, it was the end of Henderson's career, for reasons unknown. He was still only 22 at the time.