This is a genuine verge movement numbered 3140 made around 1700 by the great Thomas Tompion, small for this period. The movement is numbered on the back plate and the front plate. The even after over 300 years is very original, unrestored, but then balance swings and ticks when pressure is applied I am sure with a service the movement will work. The ringed balance wheel is typical of Tompion movements of this time, the movement is listed in the Jeremy Evans book Thomas Tompion at the Three crowns.
Back plate diameter 35 mms. Dial plate diameter 37 mms.