73 Midget ignition key

Can someone help my feeble mind and explain how I SHOULD be able to remove
the ignition key from the lock assembly.  The assy is removed and the key
is in the lock.  The oval button on the face of the slot allows the key to
turn.  What's the small brass colored pin on the outside edge supposed to
do? I'd like to gety one, or both, of these working. Thanks
Dick B.

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