Fascinating to see the 8 various types of hole punches different card index systems may have used on their index card filing cabinets.

Advertisement from System, December 1906:

CARD INDEX SYSTEM <br /> If you are using Card Systems, as manufacturers we are in a position to save money for you on these supplies. We make suggestions to anyone desiring to install labor-saving-money- making Card Systems.<br /> Cards supplied for all makes of cabinets.<br /> Write for prices and estimates.<br /> STANDARD INDEX CARD CO.,<br /> 707-09 Arch St., Phila., Pa.