According to Staffan Kinman’s excellent European Makers of Edged Weapons, Their Marks (2015) the mark Z B is for Zeughaus Bern from around 1540. 
 
If you consult Schneider’s Waffen im Schweizerischen Landesmuseum (1980) you may find what Z S stands for.
		 
		
		
		
		
		
		
		
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