Silver English Lever Pocket Watch
This Silver English Lever Pocket Watch is a later example from the early twentieth century.
The case bears the anchor hallmark for Birmingham with the date letter, t for 1918
The temperature compensated balance wheel is contained within a removable casting which is not unlike the platform escapement. The double coil hairspring was developed by Breguet to improve accuracy.
It is made to be robust and reasonably accurate.
There are plenty of resources on the internet to identify hallmarks, The Britsh Hallmarks Guide website is worth a look.