Unusual Silver Calendar Verge

An early 19^th Century French verge with calendar and seconds in a silver drum shaped case.  Full plate gilt fusee movement.  Finely pierced and engraved bridge cock with steel coqueret, plain three arm gilt balance with blue steel spiral hairspring.  Silver regulator dial with blue steel indicator.  Wound through the signed white enamel dial,  subsidiaries for seconds, date and day in French. Arabic numerals, gilt subsidiary hands, blue steel hands.  Unusual drum shaped plain silver open face case, the top plate of the movement almost as large a the dial plate, movement secured by two screws.  The back with maker's mark "J - B  over "M" in a diamond and French hallmarks.