The MB&F Legacy Machine Perpetual 03.SL.S features a stainless steel case measuring 44 mm in diameter and 17.5 mm in thickness. The movement, developed by Stephen McDonnell, includes a fully integrated perpetual calendar with a dial-side complication and a mechanical processor system with a built-in safety mechanism. It is manually wound with double mainspring barrels and has a bespoke 14 mm balance wheel with visible traditional regulating screws. The dial is an openworked salmon face, and the caseback is sapphire crystal. The strap is hand-stitched alligator leather with a stainless steel folding buckle.