What country code is XT?

Excuse me, could you please clarify something for me? I've come across the country code "XT" and I'm having trouble identifying which country it corresponds to. I've looked through various sources, but I'm still unsure. Could you possibly shed some light on this for me? Is "XT" a valid country code, and if so, which country does it represent? I'd greatly appreciate any information you could provide.