Cutter

http://www.uiowa.edu/~libsci/faculty/cotton/122-cutter.htm

Some interesting notes here on Cutters eg.

The Cutter number "D557" comes between D55 and D56. ie D55 = D550 but the 0 is dropped.

The "3 figure tables" do not use D55, but goes from D549 to D551.