Cello Lock

This lock is not very difficult to open, so it probably doesn't really count as a puzzle lock, but I like the musical motif.  The arm is the locking pin which can be removed when the key is inserted correctly in a hole at the base.

Chinese Brass Lock

Many mechanical puzzles are just for the fun of solving them.  This puzzle is designed with a practical purpose-- to thwart thieves.

Click solution to see the rather complicated process to open the lock.