After reading up a bit on tanning techniques, I am fairly confident the word in question is _Weißgerbers_ , i.e. the genitive case of _Weißgerber_. This term denotes a tanner ( _Gerber_ ) operating with mineral salts, it seems primarily aluminum salts, in order to produce leather of higher quality and lighter color ( _weiß_ = white) than more common tanning techniques.
Addendum: The corresponding English word seems to be tawer, the technique itself is called tawing.