Answer: the speth are not jewish but goths, registered members of the Gotha, the German nobility book. Actually von speth, they develop after the original registration of the family title in the 13th century, two branches, the von speth and the von speth schülzburg. As far as I know, the first disappears and remains the second until now. Their properties were in Schwaben, which was an independent territory still a hundred years ago and was integrated into Bavaria after. They even had a castle that was burned down at the end of the XIXth. Freiherren until the restructuring of nobility around the XVIth, they become barons after.