The 5712/1A is the Nautilus with complications: besides hours and minutes it shows a power reserve, a pointer date, a moon phase and small seconds, arranged asymmetrically on the dial. Patek Philippe introduced it in 2006, together with the 5711/1A.
The 40 mm case has the familiar Nautilus shape with the octagonal bezel and the integrated steel bracelet, yet it is somewhat thinner than one might expect given the number of indications.
The reason is the movement: self-winding calibre 240 PS IRM C LU has no central rotor but a gold micro-rotor set into the movement itself. This keeps the movement flat, and the finishing can be seen clearly through the sapphire caseback.
The letters in the calibre name stand for the small seconds, the power reserve, the date and the moon phase.
On a pre-owned 5712/1A we check, in addition to the finishing of case and bracelet, that every indication works correctly and can be set: the date and the moon phase are adjusted with correctors in the case flank. We compare the numbers with the certificate and state whatever we find.
More on how a watch is assessed can be found in our guide to having a watch valued.