The file HISTO.DAT contains data which can be used to generate a histogram of the number of spectra of comet Giacobini-Zinner archived by the International Halley Watch Spectroscopy and Spectrophotometry Center. The file contains two columns of numbers, the first is (Julian Date - 2440000), the second is the number of spectra in the archive for that date. Each day in the Julian Date interval, 2446145 to 2446414, 20 March to 14 December 1985, is listed. These are the inclusive dates covered by the comet P/Giacobini-Zinner data submitted by the IHW-SSN. This file was written with a FORTRAN format of 3X,2I10.