Black Flag with white TW. What is it?

[Yellowezzy]

On GTA and some of the recent TTs I have noticed that some users national flags show up as a black flag with the white letters TW. Eg Current TT Nurburgring, ranked 61st ZERO-BIM.
Does anyone know what this flag is? Just wondering as I've never seen it before.

 

[Famine]

Taiwan.