Michael Mark writes:
“These were reputedly invented by Thomas Bright Wilson of Manchester around 1880. The earliest version I have found is two carriage clocks on a see-saw stand positioned so that only one can work at a time. An apparant prototype for this with details of patents applied for in 1880/1 is in my collection.
A version of these two carriage clocks was produced by Fattorini & Sons of Bradford. The earlies advertisment I have found for this is from the 1888 British Chess Magaine...The 1888 advertisements contain recommendations for the clock dated 9 and 21 September 1887 and referring to their use in a recent Yorkshire-Lancashire match...
‘ Each pair of players was provided wiht an ingenions time-keeping contrivance, which consisted of a couple of small clocks, one at each end of an inclined bar which worked on a pivot, each clock being set going and stopped at the will of the players, by the elevation or depression of the end of the bar upon which it was fixed. The purpose of these timekeepers, which were supplied by Messrs Fattorini & Sons, was to register the time occupied by each player in making his moves, the time-limit rule of twenty moves an hour being applied to this inter-county match for the first time.’
This description suggests that this form of clock had only recently been introduced and that the writer was not familiar with it.”