Here are the simplest ways to identify your Xbox version.

If your consoler has a single row for the PSU, and the controller connectors on the front of the console have a separate PCB that plugs in to the motherboard, it is a v1.0.

If your console has a single pin row header, but the controllers plug straight into the motherboard without a separate PCB, it is a v1.1.

The only real difference between 1.2 and 1.3 is the LFRAME (pin 3) of the LPC header (where you connect mod chips) disconnected, although not visibly. There is no other real difference.

If you have a 1.2 or 1.3 model, you will have a double row power header, and a Conexant video chip.

The only difference between 1.4 and 1.5 is the 1.5 has pins 2 and 9 disconnected on the LPC.

The 1.4 and 1.5 version have a double row power header, and a FOCUS video chip.

The v1.6 will have a dual row power pin header, the EEPROM next to the LPC port, and an Xcalibur video chip.