From the miller web:

Auto line power management tecnoligy circuitry automatically connects to 115 - 230 VAC, single-phase power without removing the cover to relink the power source.


Wonder what type of plug it has.

This tig is a newer type that only weighs 13 pounds and my guess is more capacitors and electronics then transformers.
Other miller units had:
Universal Location Flexibility
Permits direct connection to almost any type of input power—115-575 VAC (varies by product), 1- or 3-phase, 50 or 60 Hz