The Q3858520 is the steel Reverso Classic Large Small Seconds: a Reverso Monoface with a single dial, small seconds at six o'clock and a solid back.
The case measures 45.6 × 27.4 mm and follows the lines of the 1931 original, with the gadroons above and below the dial and a case that swivels in its carrier.
Inside is calibre 822/2, a rectangular hand-wound movement made by Jaeger-LeCoultre itself. Because the watch is wound daily, we look particularly closely at the crown and the winding on a pre-owned example.
The solid back is intended for engraving; many examples carry initials, a date or a coat of arms.
During the inspection we turn the case over several times and check for play, for wear on the sliding rails and on the pivot of the carrier, and for a latch that holds the case firmly in both positions.
The gadroons and the edges of the case quickly show whether the watch has ever been polished inexpertly. We always state whether there is an engraving.
What a complete set includes is explained in our guide to box and papers; other Reversos can be found under Jaeger-LeCoultre.