New old stock (NOS).  Selling a  Sentrol 2507-AH-L/2507-AH mount switch and magnet.  Complete set with hardware and instructions.  It can be used in either a open or closed LooP type.  SPDT electrical configuration.  Gap Distance is 3/4" minimum to 2-1/2" maximum.  Gap distances are nominal make distance plus or minus 20%.  Comes with a 3' stainless steel cable. From the Sentrol 2500 series.  Free shipping in the USA.