The size is S. Since it has the name Sumitomo Metal Industries, I believe it's a product from before 2012 when it was integrated into Nippon Steel. Regarding points of concern during inspection, there is some peeling at the folds of the printed area (indicated by the pink circles). Also, there are some irregularities, like unevenness, especially in the black parts of the TOSTEM logo in photo 4 and the YellowHat logo in photo 9. While there is a sense of use when viewed closely, it's a relatively clean item when viewed from a distance.