If you bought an X-Mag from the AGD US Booth at IAO, WC or any other US tournament, then it will be a US version.
AGD US have sold a small number of X-Mags pre Dec 9th.
However, if you bought the X-Mag from a player, then you would need to check the ACE, as it could be a Euro version that found it's way over there. You can also contact either AGD US or AGDE to check the serial number.

We're still receiving calls from customers who don't understand what the difference was between Euro & US X-Mags
pre Dec 9th. The main difference is the ACE. When we developed Version 1 of the ACE over here, we initially used a wiring loom. The Ver 1 ACE works the same as the Ver 2 circuit board ACE, but we (AGD US & AGDE) decided to change to the circuit board because there were some concerns that the wires could get pinched or cut, if care wasn't taken, when the marker was stripped & re-assembled. As from Dec 9th, all X-mags worldwide will ship with the new Ver 2 ACE circuit board. If you have an X-Mag with the Ver 1 ACE, it does NOT mean that you have a Beta X-Mag. Your ACE works the same as a VER 2 ACE. It has the same components, and uses the same version of the ACE software.
We only shipped Beta X-Mags to specific players, who were happy to participate in the Beta program. Beta X-Mags were used to try out a variety of new ideas & specs, but the Beta markers are all kept updated to the latest spec.
I hope this makes things a little clearer.