A common problem with magnet bases is that the plastic switch breaks, here is a replacement switch and a STEP file if you want to change it. 

Should work with all 50mm wide models of magnet bases, Noga, Mitutoyo, Eclipse, Diesella and all brands. The magnet base is most often used for dial indicator arms and other measuring equipment. Used by machinist or other craftsmen.

Print with support and 0.2 layers, 8 perimeters, i printed my in PLA and it has survived but PETG would be better.