IBM Vintage Single Stitch T-Shirt - There is a little light pilling and a little light soil but I think most of the discoloration you see if from the lights that don't balance well with light blue. The tag has been removed but it's light weight and single stitch

34 1/2" Chest is generally on the smaller side of small

Shoulders 15 3/4"

Chest (underarm-underarm) 17 1/4"

Length (shoulder-hem) 25 7/8"

Sleeve (shoulder-hem) 7 1/2"