This is possibly the best burr puzzle ever invented. Bill designed it by hand when he was 16 years old. (so, a looooong time ago :)

Intended as a take-apart puzzle, disassembly is very tricky with many many false starts and dead ends. Reassembly is of course very very difficult. I don't generally include instructions, but I will gladly send the directions to this one should the buyer wish (just email me).

Here's how he describes it:
The puzzle consists of 3 parts:

1) The 'innards' - 24 pieces in the standard 24-piece burr shape 2) The 'shell' - 41 pieces, mostly surrounding the 'innards', which fill out the cube shape, and also form the locking mechanism to hold everything together 3) The 'key piece' - the cross-section of this piece is rectangular - half as thick as the other pieces which are cut from a square rod.