A postmark shows from what town, and on what date, an item was mailed; most postmarks also cancel the stamp. Simple straightline postmarks consist of lines of type. Most of the Wiesenthal postmarks are the more familiar circular date stamps (CDS).
There are almost as many ways to collect postmarks as there are collectors. Some prefer postmarks with a specific theme. Others specialize in socked-on-the-nose (SOTN) or bullseye postmarks — those which are complete and well-centered on a stamp. Still others look for postmarks from their hometowns. Simon Wiesenthal's search for towns that shared his last name was a twist on that idea, although the Wiesenthals he found were far from his own birthplace in what is now Ukraine.