Gage Master Corporation Calibration Kit for Optical Comparators. Included in the accessory box are: Scale Frame 4" X 4" traceable glass master linear calibration scale, screen overlay, lens magnification checking scale, precision square, screwdriver for lens magnification set screw release, 8X eye lupe, and procedure manual. The last certification of this kit occured July 2000. This kit can be used on all Optical Comparators to assure the accuracy of measurements.