That was my question when I first saw the stamp! Then I realized the vertical parts of the H are stamped as wide outlines while the horizontal bar is a single line.
Based on Musial's career ending in 1963, I'd guess this glove is from the very early 60's, but the pattern and construction are more like late '60's or early '70s. Maybe it was released around the time he was voted into the Hall of Fame in 1969. I claim ZERO expertise about gloves or Stan Musial, so don't put stock in what I say. My uncle had a six-finger glove from the late '50s/early '60s, and it seems like it was a Musial model. I got my first glove in 1963(?) - a Jim Davenport model Wilson. Gloves from that time looked a lot more like updates of gloves from the the late '30s, '40s and '50s than this glove does.
At any rate, it's probably 50 years old or more. Great glove!