Tudor Black Bay GMT Watch, 41mm Black Dial, M79830RB-0003The Black Bay GMT is an extension of the Black Bay line with a highly functional complication: a multiple time zone function also known as a GMT function. Recognisable by its rotatable bezel, which derives its deep blue and burgundy colour theme from other models in the Black Bay line, but in a matte version, the Black Bay GMT is also a nod to the early days of this watchmaking function.