18th Century English Calendar Verge

A late 18^th Century English verge with calendar in silver pair cases.  Full plate fire gilt movement with round pillars.  Pierced and engraved cock, pierced and engraved foot and plate for the silver regulator disc. Fusee and chain with worm and wheel barrel setup between the plates. Plain three arm steel balance, blue steel spiral hairspring.  White enamel dial with central indication for day of the month,  Roman numerals, blue steel beetle and poker hands.  Matching silver pair cases, silver pendant and bow, maker's mark "SP" in a rectangle and number corresponding to that on the movement.