Complex sentence: Certainly from around 1711 it was George Graham who was in partnership with Tompion, some of his later productions are jointly signed, and mysteriously some clocks have this signature on a separate plate which overlays that of Tompion and Banger engraved on the dial plate proper.
Split into simpler sentences: Certainly from around 1711 it was George Graham who was in partnership with Tompion. Some of his later productions are jointly signed, and mysteriously some clocks have this signature on a separate plate which overlays that of Tompion and Banger engraved on the dial plate proper.