Brass Single End Clock KeyAvailable in many sizes, this is the most popular choice on this page.
To get the key you need, measure the shaft the key is to go on to, then use this chart to get the key size # you need. Please do not call asking what key your clock needs, as you will be told it would still have to be measured. Again, you are measuring the shaft that the key goes onto in MM and then using the chart on our keys page here.
Almost all post 1960 mechanical clocks, made in Germany take a size #8 key or crank, unless the movement is round. The round ones take a number 4 usually.