Mechanical clock keys
Mechanical clock keys is the clock part that is most frequently lost. Once the clock key is separated from the clock it always seems to end up missing. With the below information and the clock key size chart a key can be ordered.
Getting the right one
We have mechanical clock keys in all the sizes available. Between the key chart or by movement type information below, the chances are good of getting the perfect key. The movement type includes if the clock is made in Germany or USA and when it was made. This is the fastest and most easiest way to get the clock key. The further back in time we go with clocks the more the key chart would need to be used instead. The country of origin would be marked on the back plate of the movement and this can help us get the key.
Keys for German units post WW2
Germany post WW2 movements that are square or rectangle will take a number 8 key or crank. If the clock movement is made in Germany and it's round the key size is number 4. Some round ones are supposed to take a number 3 but if you get 4 it will still fit and wind the clock either way.
Keys for USA units 1900 - 1950
American clocks made from around 1875 until after the second war almost always take the size 7 clock key. The number 7 keys fits the 8 day time / strike units pretty much every time and this is what USA made the most of. This rule may not apply to Westminster (3 places to wind) or time only (one place to wind) clock movements.
Keys for Korean and Chinese clocks
Size 7 for these units usually. All the 31 day clocks with Asian movements and also US replicas made in India, all take size 7.
The over wound myth
Of course any clock that is not working will be wound all the way up from trying to make it run. Everyone winds it up and the clock does not work so the non working clock is always wound up. The only way a clock can be over wound is if its been wound up for so long that the mainspring stuck. When the mainspring is stuck together to itself with rust and goo for so long it may stick that way. This is rarely the situation and usually the clock would have rust on it if the mainspring is so wound up it will not wind down.