The type of power supply can be identified by the label at the rear panel next to the mains inlet. 

• If the type plate or sticker says "100 - 240V" A-100PSU3 is installed.
• If the type plate or sticker says "220 - 240V" or "100-120V" A-100PSU2 is installed.

The main difference is that the A-100PSU3 has a wide range mains input that can be used with any mains voltage in the range from 100 to 240V AC. A-100PSU2 is suitable only for 230V (range 220-240V) OR 115V (range 110-120V).

In addition you can find out if an A-100PSU3 or PSU2 is installed by looking at the pictures of the power supplies in the A-100 Accessories page