He signed the back of the card in ballpoint pen. I guess he signed the back because he may have thought the pen wouldn't show up on the front. Still, I am happy the card got signed.
Hinrichs (b. 1925) played in the majors in 1951. He appeared in 4 games for the Red Sox. He holds no win-loss record, had one strike out and a 21.60 ERA.
I mailed to Hinrichs on May 10 and got the card back on May 18, for an 8-day TAT.