Hesalite Moonwatch

The Speedmaster Professional is a watch with a built-in stopwatch. It has a black face, three small dials and two buttons beside the winding crown. The steel 3570.50 is a version from the mid-1990s, sold under the name Moonwatch. Its shape comes from watches made decades earlier.

The long hand in the middle is the stopwatch's seconds hand. It normally rests pointing straight up until the upper button starts it. The watch keeps running while that hand is stopped: ordinary seconds appear on the small dial at nine o'clock. The other two small dials count the minutes and hours of whatever is being timed. This is why the Speedmaster needs so many hands.

It began as a watch for racing drivers. When Omega introduced the first Speedmaster in 1957, it put a speed scale around the outside of the face. Time a car over a known distance and that scale, called a tachymeter, lets you read its average speed. NASA later tested the watch for a very different job, qualifying the Speedmaster for spaceflight in 1965. Earlier versions accompanied the Apollo astronauts to the Moon in 1969.

The 3570.50 came much later. It kept the black dial, the three small counters and the steel case that extends around the crown and buttons on the right. At 42 millimeters across, there is room to separate the different readings. There is no calendar window among them.

It also kept manual winding. Turning the crown tightens the mainspring that powers the watch; movement of the wrist does not do that job. Omega's archive lists both the 861 and later 1861 movements for this reference. Neither name should be confused with the earlier 321 used in the lunar watches. The Moonwatch name connects generations, not identical mechanisms.

From the outside, the cover over the face is a more immediate distinction. Omega calls it Hesalite: acrylic plastic rather than sapphire. It rises above the black rim and curves down around the dial's edge. This generation kept that raised acrylic front even after sapphire was available for watchmaking. On the other side is a closed steel back; the watch's mechanism is not on display.