The Jaeger-LeCoultre Master Ultra Thin Réserve de Marche Steel Blue Dial 39mm Ref. Q1378480 combines advanced functionality with refined design in a slim profile. This 39mm stainless steel model features a sunburst blue dial with applied indexes and a clear layout that includes a power reserve indicator, date, and small seconds display. The case is topped with a scratch-resistant sapphire crystal and paired with a matching blue alligator leather strap, secured by a stainless steel folding clasp for added comfort and security. Inside, the selfwinding Jaeger-LeCoultre calibre 938/1 movement delivers a 40-hour power reserve and features 41 jewels for smooth operation. Water resistance is rated to 50 meters, offering versatility for daily wear. Notable highlights include the ultra-thin construction, practical power reserve complication, and the striking blue dial, making this Master Ultra Thin Réserve de Marche an excellent option for those seeking a classic dress watch with useful added functions.