QM7221

QM7221 Non-Contact Thermometer with Dual Laser Targeting is an IR Thermometer sold in Australia by Jaycar Electronics.

Almost certainly a re-badged Extech 42511 or similar device, which itself may have been re-badged from somewhere else.

Disassembly

open battery case and remove 9V battery
remove battery case lid by gently prising away from body of device
remove two Phillips head screws, one near trigger and other inside of battery cover pivots
prise off bezels at front and surrounding LCD (latter retains rubber buttons, so don't lose those!)
gently prise two body halves apart
electronics on three PCBs can be separated from body halves
remove two screws securing heat/electrical shield from back of sensor, releasing lens assembly

IR detector is a device in a 4-pin TO-39 style case.