Sold Leica Barnack bottom plate

I have a bottom plate for a screwmount Leica camera in excellent condition only light marks on finish. The problem is I don’t remember for which camera. It came off of one of the many Barnarks I used to shoot and own. I have an IIIF and it mounts but cannot lock. I don’t know what that means so take a chance if you are interested.

$50 plus $10 for USPS Priority shipping.