The stopwatch pictured is one of the stopwatches designed and manufactured by Seiko for use at the 1964 Tokyo Olympics.
It is one of the standard stopwatches, not intended for any particular sport or event.
It measures up to 10 minutes and can measure time to 1/100th of a second.
The large sweep hand goes around the dial every 3 seconds. The inner dial measures up to 10 minutes and the sub-dial at 12 o'clock is a 60 second dial.
The outer scale allows time measurement to 1/100th of a second.
It is fascinating to watch the speed at which the sweep hand traverses the dial.
This model, along with others, some designed for particular sports, appears in the Seiko 1964 catalogue.
Among others, a similar model is also displayed in the Seiko Museum.