This A. Lange & Söhne Richard Lange Perpetual Calendar "Terraluna" is among the most ambitious and beautiful watches the manufacture has created, a two-sided astronomical masterpiece whose reverse is as compelling as its face. The front follows the regulator layout of high-precision scientific clocks, with separate displays for hours, minutes, and seconds, alongside an instantaneous perpetual calendar with outsize date and a fourteen-day power-reserve indication. Turn it over and the movement side reveals its signature: a patented orbital moon-phase display showing the moon circling a globe, so accurate it would take over a thousand years to drift by a single day. Powered by the hand-wound calibre L096.1, it also carries a constant-force escapement to steady the delivery of energy from its twin barrels. The white-gold case measures 45.5mm across and 16.5mm in thickness, substantial in the manner its mechanical depth demands. A silver dial lends clarity to the wealth of information. A landmark of modern astronomical watchmaking.