The Hamilton MIB II has an LCD, not LED display.
The display contrast is quite poor, this has been discussed here before: http://dwf.nu/viewtopic.php?t=2149&highlight=MIB and http://dwf.nu/viewtopic.php?t=1874&highlight=mib
When the battery gets empty the green backight becomes very dim and also the LCD vanishes when you press the light button. Try and change the battery.