Letter from Frederick Cohen Regarding a Burglar Alarm System Installation, Philadelphia, Pennsylvania, March 1, 1888 A letter from Frederick Cohen, dated March 1, 1888, apologizing for the delay in installing a burglar alarm system. The letterhead features an illustration and the business information: "ELECTRICITY IN ALL ITS BRANCHES...ELECTRICAL & GAS LIGHTING.....CALL BELLS & BUGLAR ALARMS", 814 N. 21ST STREET, Philadelphia, Pennsylvania.