It was made c.1916 by Nicole Nielsen, Soho Square London and signed 'Chas. Frodsham 27 South Molton Street No.09571 London' on a silvered dial. There is a start/stop push button in the pendant. The outer dial is for 0-60s marked every 5, and the inset dial is marked 0-100 in 1/100th second intervals. There is a flush winding button recessed into the back cover.
The movement, with six jewels and a cylinder escapement, has a very small balance wheel beating 72,000 per hour. The watch, which is stopped by a small 'finger' contacting the balance wheel rim, was use for accurate duration timing (up to 60 seconds) such as the timing of projectile flights.
From Antiquarian Horology, December 2002.