 Complete the following phrase:  Delettrez and Achille Brocot, son of the respected clockmaker Louis-Gabriel Brocot, established the clockmaking company Brocot et Delettrez in Paris on 20 October 1851, with premises at 62 Rue Charlot. Delettrez worked alongside Achille Brocot for several years and their clock movements are considered to be the most effective made during the late 19th century.  Their speciality was a range of clocks based on the innovations of Brocot père and his other son Antoine, but generally of Achilles greatly advanced original design, some having a unique single-arm double-wheel escapement, some having a temperature-compensated pendulum, some having two dials, one of which showed the time and the other which showed a calendar and often other information such as phases of the moon, times of sunrise  sunset in Paris, etc. The firm was awarded a 1st class prize at the 