The Q1368420 is the steel Master Ultra Thin Moon, with a 39 mm case and a silvered dial. It is a classic dress watch: a thin round case that slips under a cuff, a restrained dial with baton indices, and a sub-dial with date and moon phase as its only complications.
Inside is Jaeger-LeCoultre's automatic calibre 925/1, visible through the display back. Date and moon phase are set via the crown or a corrector; if the watch has been standing for a long time, both need to be set again.
On a pre-owned example we look at the polished case, on which scratches and polishing marks are easy to see, at the thin edges of the case and at the crystal.
We test the automatic winding, the setting of time and date and the advance of the moon phase, and we compare the reference and serial number with the papers. A thin case is more vulnerable to inexpert polishing, because there is less material to remove.
What a complete set includes is explained in our guide to box and papers.