Victor Kullberg was born in Sweden, he apprenticed in 1840 and worked as journeyman to the famous Swedish watchmaker Urban Jurgensen in Copenhagen. He then moved to London in 1851 initially making top quality escapements for other clockmakers but he soon began to supply complete watches and chronometers. besides being a brilliant clockmaker, he was also an astute businessman and his career flourished, helped considerably by success with his movements at the International Exhibitions and Time Trials. At the Greenwich Time Trials he won no less than three times - not including one year when two of his movements came joint first.
In 1864 Kullberg won his first Greenwich Time Trial with chronometer No. 760 which, for the first time, was fitted with his flat rim balance. Famed for its clever ability to compensate for temperature error, the flat rim balance also had arrestingly good looks. The Astronomer Royal, in his report to the Clockmakers' Company on the subject of chronometer 4066 by Kullberg which had again won first prize said ...that this was the finest chronometer they had ever had on trial.
The flat rim of the balance is brass fused onto steel. The cross-bar has the brass on top, the rim sectors has the brass beneath. Very heavy wedge weights are carried on raised portions at the free ends of the rim sectors. In the heat the ends of the cross-bar dip, raising the weights, and the rim sectors flex, also raising the weights. The combined motion causes the weights to describe an arc of circle vertically, towards the balance axis - in cold the reverse happens. His balance worked brilliantly but like many good inventions it was very expensive to make and surviving examples are extremely rare.