I thought I had one somewhere.
Very similar to yours although mine has slightly different decimal dial.
The "switch" at the side turns the movement on, press the crown and the count starts. When the observer has witnessed 10 or howeber many operations/sequences thet hit the crown again and the count re-starts for the next sequence.
When enough readings have been taken, the switch is set to off and the sweep hand is retuened to zero.
Readings that were noted allow quick calculations to be made based on decimal numbers rather than the complication of calculating X operations in 32.5 seconds to arrive at a rate of effort (for example).
