Key combinations listed below work as described on Andrew's GM100. They may or may not work similarly on other LEI receivers. Consider yourself warned, the risk is yours...
Press: MENU, select SYSTEM SETUP, select SYSTEM INFO, press DOWN 5 times “Time Used” screen should appear.
From “STATUS” screen go “DOWN” 5 times.
From “STATUS” screen go “UP” 5 times.
Press the MENU key and POWER key together. Right away after the GPS powers up press the MENU and POWER keys together again.
Hold down the UP and DOWN arrow keys and press the POWER key, continue to hold down the arrows for a short while after. The self test screen indicates (hardware?) version. Mine is 1.83