This and the Tern Key make a nice pair of grey-code puzzles. The goal is to remove the bottom key from the lock by manipulating the traped sliding pieces in the frame. The solution takes 85 moves and is non-trivial.

Here is what Pit Khiam has to say about the puzzle: "Binary Key II is a redesign of my Key Puzzle. The original puzzle was designed to be minimalist but I felt some of the pieces could be changed to make them slide better. The key piece is now made shorter and the number of rings has been increased to 5 instead of 4. Of course, the number of rings can be increased indefinitely but would only make the solution to the puzzle more tedious. The following table shows the relation between the number of rings n and the number of moves Tn to solve the puzzle."

Precision cut from solid cast acrylic and painstakingly hand assembled, this puzzle has a nice weight/feel, and will not be confused with cheaper mass produced take apart items. The construction uses contrasting press fit dowel pins to align the internals, and the push pins are stainless so they do not corrode over time. 40 total copies made for sale.