Finder graticules are used to swiftly and accurately give a position of reference to an area  of interest on a specimen slide. 

The England Finder - 9045 Findable Locations 

The England Finder is a glass slide marked over the top surface in a way that a referenced position can be directly read relative to the locating edges. 

All England Finders produced by Graticules for over 40 years are identical. The purpose of the  finder is to give the microscopist an easy method of recording the position of a particular field of  interest, so that the same position can be re-located at a later date, or by another person in another  laboratory, or when using any other England Finder on any other microscope. 

The location of the arrows is identical for all England Finder slides. The method of use is as follows: Mark a label on the left hand side of the specimen slide, indicating the orientation to be repeated.  By replacing the specimen slide with the England finder, taking care not to disturb the position, the  feature of interest can be noted. The feature can also be re-located at another place or time by  reversing the procedure. A total of 9045 positions on a 76mm x 26mm.