Default How can I know the GSM channel using?

Hi, I get a XDA in bidding, which I don't know if it GSM(900/1900) or GSM(900/1800) . He claim that it is GSM(900/1800) from UK, but I can't use it in HK, so I think it is GSM(900/1900) from US.

The case of XDA is yellow, is it mean it is from US?