The Duplex watch escapement shown in the images below was invented by Robert Hooke circa 1700, then later improved by Jean Baptiste Dutertre and Pierre Le Roy, before being perfected by Thomas Tyrer, who patented it in 1782. The Duplex escapement was difficult to make but achieved higher accuracy than the Cylinder escapement, which was also a 'Frictional-rest' escapement. This meant there was additional friction compared to the lever escapements that would end up dominating future movements. It was used in English pocketwatches as the one shown here, between 1790 to 1860.

An independent bridge supports the balance spring, above the balance cock.

The balance assembly removed, revealing the hidden Duplex escape wheel.

Close up of the escape wheel that directly contacts the balance wheel with no in-between anchor/lever.

The underside of the balance wheel showing the lever that is impulsed by the upper escape wheel teeth.

Profile showing the two levels of the balance staff assembly that come in contact with the Duplex escape wheel.

The timepiece also includes a thermometer, below you can see the full mechanism, normally hidden under the dial.

The rack and pinion system driving the thermometer hand.

The long ‘n’ shaped piece at the bottom of the movement is a made from steel and brass (like the balance rim) and moves with the change of temperature acting on the rack and changing the indication of the temperature.

Thanks to the The K&H Watchmaking Competence Centre for the loan of this movement.