The 79030B is the Black Bay Fifty-Eight Navy Blue, introduced in 2020. Case, size and movement are the same as those of the black 79030N: 39 mm steel, water-resistant to 200 metres, and the in-house calibre MT5402 without a date, with about 70 hours of power reserve and a COSC certificate.
The difference lies in colour and finish. Dial and bezel are navy blue, and the gilt accents of the black version gave way to silver-coloured hands and indices. That gives the watch a cooler, more modern look, while the proportions that make the Fifty-Eight so wearable remain unchanged. The Navy Blue was supplied on a steel bracelet or on a strap.
On a pre-owned example we look at the blue aluminium bezel, on which scratches and, after years in the sun, fading can become visible, at the luminous material, at the bracelet and clasp, and at the completeness of the set. For a version on a strap we state whether the original buckle is present. If you are torn between blue and black, you can compare both versions with us when they are available, or give us a sourcing request.