Glenn Herbert wrote:"Ball peen" is the full term for it. There are also cross peen and long peen hammers, which have a rounded narrow rectangular face opposite the regular hammer face, for making marks crosswise to or parallel to the handle.
Not to get too far off-topic here, but yes.
AND, you'll find them all spelled "pein" instead of "peen" sometimes, too. And in my circles, a pein hammer with the narrow face parallel to the handle is a "straight-pein" rather than "long peen". But obviously, these things vary from place to place.
Thought I'd chime in, because so often the key to finding what you need is knowing its name!