This beautiful-looking tool is called a Latthammer, and it's Germany's version of the carpenter's hammer. The square head ("for greater precision," as Picard's booth representative explained at Holz-Handwerk) is the first thing you notice, and then a closer look reveals this groove at the top:
The sales rep's English wasn't great and my German is non-existent, but through pantomime he explained what it was for. There are times when a carpenter needs to drive a nail in a location over their head, where they cannot reach their other hand up to steady the nail. In these cases, the nail is placed into that groove, where it is held fast by a magnet. The carpenter can then single-handedly whack the nail into the surface far enough to get started, and can then drive it in the rest of the way with the same hand. Observe:
I call that brilliant.
Picard is a German tool manufacturer that's been around since 1857, by the way, and they make every type of hammer you can possibly imagine.