Clock Mainspring Let-Down Tool
Used to release the power in a wound up mainspring, this a Clock Mainspring Let-Down Tool. Key goes into the chuck and the chuck goes into the handle so the power can be let down one the mainspring. It does the same job as the let down with all the chucks that is also offered, this one fits over the existing clock key instead. If someone were to take a spring driven clock apart without letting down the mainsprings, bad things may happen. The movement could be damaged, it can hurt someones hands, so for this reason the mainsprings power always needs to be released.