While it may look like one of them fancy metal detectors you see folks walking around on the beach with, this is in fact the long-obsolete Syncro fuel level sending unit! Yep, these things went the way of the dinosaur a few years back, but thanks to some kind folks in Germany they are back in production.
If your fuel gauge is reading incorrectly, or not all, this is most likely the culprit. Make sure you order two new sender gaskets, as well. Sold separately below.