De Bethune DB25 Moon Phase With Silicon Balance Wheel

This latest addition to De Bethune’s DB25 family is fitted with a new hand-wound mechanical caliber with a six-day power reserve, based on the DB2105 movement. The silicon balance wheel, used for the first time in a production movement, is the product of research undertaken since 2002 focused on improving the oscillator. Together with the balance spring with the De Bethune flat terminal curve, the two form an oscillating assembly that marks a new step forward in the quest for isochronism, a precisely uniform rate.

The 44.6mm drum case in rose or gray gold houses a silvered gold dial with hand-applied guilloché. The famous De Bethune spherical moon appears through the dial against a sky that is flame-blued by hand and dotted with gold stars. The moon consists of two hemispheres, one in flame-blued steel and one in platinum, and it rotates on its own axis, reproducing exactly what you would see in the sky. The moon-phase display is accurate to within 1 day in 122 years.

The technical description appears below the image, which can be enlarged with a click.

Technical description

Material: rose gold or white gold
Case: drum
Case dimensions: 44.6mm in diameter and 11.1mm thick
Dial: silvered, guilloche by hand
Hands: flame-blued steel, hand-polished
Crystal: sapphire, 1800 Vickers hardness with double anti-reflective treatment
Crown: screw-down at 3 o’clock – settings in 3 positions
Movement: DB2105si – hand-wound mechanical – decorated and “colimaçonné” by hand, steel chamfered and polished by hand – self-adjusting double spring barrel – silicon annular balance with flat terminal curve
Functions: hour, minute – moon phase indication – power reserve indicator on the back
Jewels: 29
Frequency: 28’800 vibrations per hour
Power reserve: 6 days