Many of the USAAF combat squadrons had their own baseball teams. Their sportswear was actual mil spec. government issue.
The sweatshirt was worn underneath the button-front cotton overshirt, and has 3/4 length sleeves.
Measure your chest over a T-shirt; it is helpful to get someone to do this for you. Do not inflate your lungs, just relax and stand with your arms out. The tape measure should be run around your chest right up under your arms and held snug, but not tight - this is your chest measurement.
Measure the circumference of your hand around your 4 knuckles (obviously do not include your thumb). Correlate this measurement with size chart below to assess your glove size.
Measure the circumference of your head.