Gave me his business card

This is actually something that now stands-out extremely strongly in my mind, when I think about this trip. When the man extended to me his arm, his sleeve on his suit jacket pulled back, and I saw some faded numbers tattooed onto his wrist. At the time the tattoos had no meaning to me, except that they were somewhat of an anomaly. It wasn’t until later, after I’d returned home and was on a "World War II" reading spree that I realized that it was likely that the man was a survivor of the concentration camps. I am actually kind of glad that I didn’t know this information at the time, because I don’t think that I would have had the maturity to know how to handle myself. Actually, I don’t know that I’d know how to handle myself now, come to think of it. How does one "correctly" respond to that situation?