Apparatus and method to indicate required compressor pressure for use with pneumatic tool device

An apparatus which enables a user of a pneumatic tool device, such as a nail gun, to determine the required compressor pressure needed to most effectively utilize the pneumatic tool device and maximize the life of the tool. A compressor pressure indication assembly on a nail gun comprising a nail verification assembly and a readout assembly enables a user to verify the length and/or diameter of the nails to be driven by the nail gun and set the compressor pressure accordingly.