Tudor Black Bay 58 Jubilee 39mm 7939A1A0NUOverview The Tudor Black Bay 58 reference 7939A1A0NU is the current generation BB58 the second iteration of the model Tudor introduced in 2018. The defining change is the movement: the MT5400 U adds METAS Master Chronometer certification to the existing COSC standard, making this the most technically specified movement Tudor has put in the BB58 to date. The 39mm case sits at 11. 7mm thick measurably slimmer than the standard Black Bay. The matte black