What key does this take?

Doesn’t take a B key.

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That is an Arrow-Hart key switch. It is a version that holds the key captive when turned to the off normal position. It takes an Arrow-Hart key.

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Is that the same as the drill key?

I had one Arrow-Hart key on my ring and it fit everything I needed it to do. There are a number of different handle types but the business end all seem to be the same.

Occasionally I had to replace a switch that was turned with some other key. Once turned the correct key could not be inserted to return the switch to normal.