The 15710ST is the steel Royal Oak Offshore Diver, introduced in 2010. Unlike most dive watches it has no rotating outer bezel: the diving scale sits on an inner ring beneath the crystal and is set with a second crown at ten o'clock. That preserves the octagonal Offshore bezel with its screws.
The case measures 42 mm and is water-resistant to 300 metres; the dial has the Méga Tapisserie pattern and a date. Calibre 3120 has about 60 hours of power reserve. The Offshore Diver was supplied on a rubber strap, in keeping with its use in and around the water. It was made until 2021; its successor is the 15720ST with calibre 4308.
On a pre-owned example we look at both crowns and the operation of the inner ring, the finishing of the case, the condition of the rubber strap and clasp, and the completeness of the set. As with any dive watch, the actual water resistance of a pre-owned example depends on the gaskets; we state it when they have been tested recently. Anyone looking for an Offshore with a chronograph will find it in the 26470ST.