Croton, Nivada, or Nivada Grenchen: by whatever name they go by, this company’s watches were meant to handle anything. And no model of Nivada's typifies this more than the Chronomaster Aviator Sea Diver; not only is it a chronograph (a chronomaster, even), but it can be used at sea and in the air. 

Nivada (called Croton in the U.S. due to a copyright dispute with Movado) introduced the Chronomaster Aviator Sea Diver in 1963 and produced it in many different flavors until 1978. The most common iteration, featured on this watch, has two chronograph registers at 3 and 9 o'clock, while later versions had the addition of a date window. The registers are black on black, with a red triangle in the 30 minute subdial for timing regattas. Nivada used broad arrow hands during the 1960s before transitioning to stick hands in the 1970s; it's the former style that you see here.

Another salient feature of this watch: the bi-directional bezel, showing 60-minute elapsed time as well as a GMT function. (Because, as you can guess from the name, this was meant to be a dive watch as well.) 

It features a 38mm stainless steel case with holey lugs, an acrylic crystal, a signed crown, a bidirectional rotating timing/12-hour bezel, and a matte black Tritium dial with a matching ‘broad arrow’ handset, a dual-register chronograph/regatta timer, a tachymeter scale, and a 1/5th-seconds track.

Powered by a robust and reliable hand-cranking Valjoux movement, this wildly cool instrument made in a virtually perfect size, is an exception and attainable example of what we think is one of the best sports watches of the era.

While these timepieces are not exactly scarce, one in this condition — and with its factory goodies — is truly a rare find.

Behold!