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The Secrets of the Heart is a puzzle from Bits and Pieces, designed by Doug Engel and sold by PuzzleMaster.
The puzzle is made by five nickel plates in the shape of a heart and a gold ring. It's quite heavy for its size, but expectable due to the number of metal plates used in the puzzle. At first glance it may look like the goal is to remove the ring, but you actually need to unlock a sliding arm from one side of a puzzle. When you do this, you'll discover that inside is a small compartment to enclose something special.
As far as difficulty goes, the Secrets of the Heart is a fairly easy puzzle to solve. It's rated by PuzzleMaster as 5 out of 10, so the easiest you can get at PuzzleMaster. To open it, you'll just need a couple of minutes to inspect the puzzle: the ring functions as a locking system and you just need to rotate it from one side to the other, in order to allow the arm to slide off the puzzle. Returning the arm to its position is even easier to do, because you already know the secret to open it, so you just need to maneuver the ring appropriately to close the heart again.
As an experienced puzzler, you won't find the Secrets of the Heart remotely challenging, but it's definitely a must for a collector, especially if you're into metal puzzles. It's very different from what you're used to see in puzzles and on top of that, a simple and beautiful design.