This article was originally published in the January/February 2022 Issue of the WatchTime print magazine. 

If you want to discreetly find out the time, you shouldn?t look at your own watch, but at the one that?s opposite you. That?s no problem at all if the person sitting across from you ? whether they?re a pilot or not ? is wearing the Sinn 717. This big watch is an on-board instrument for the wrist. It?s an enormous 45 mm in diameter, but size isn?t the only reason why it?s so easy to read. Its dial is indeed based on the face of an on-board clock, Sinn?s historic NaBo 17 ZM. The ?ZM? here stands for Zentral-Minute, which is German for central minute, but we?ll say more about this later. Even in the dark, this watch is easy to read and, thanks to anti-reflective coating on both sides of the sapphire crystal above the dial, the face remains legible even under challenging visibility conditions and from different angles.
Sinn?s owner and managing director Lothar Schmidt told us that a pilot had sent him a historical NaBo 17 ZM that had been salvaged from a crashed aircraft. But this wasn?t the inspiration for the 717. Before that, one or two customers had asked him to reissue the old cockpit chronograph. Schmidt gave the matter some thought and decided that it would be a good idea for the company?s anniversary. After all, the company became known for pilots? watches and on-board clocks in the early 1960s.

The NaBo 17 ZM was developed toward the en...