The 2x2 Burr is the design creation of Osanori Yamamoto and the puzzle was also Rosemary Howbrigg's IPP35 Exchange Puzzle.
The 2x2 was produced for Rosemary by Mr Puzzle and its a 4-piece puzzle made of Western Australian Jarrah for the wooden pieces and 10mm thick acrylic for the remaining two. The 2 wooden pieces are identical while the acrylic slabs have different shaped cut-outs for each. Construction fit and finish is very good and the wooden pieces are strengthened at the joints with bamboo dowels even. Very nice touch.
The puzzle came un-assembled and the object is to fit the pieces together to form the symmetrical shape as shown in the photo. I didn't think it would be that difficult looking at the cut of the pieces, after all, Rosemary's Exchange Puzzle to me at last year's IPP34 the 4-piece "Black Hole Burr" only took me less than half hour to solve. But I was dead wrong. This one is a lot harder!
Firstly the assembly of the pieces cannot be achieved in orthogonal fashion; meaning moving the pieces left right up and down against each other. Instead, putting the puzzle together requires multiple rotational movements. And this is something that Burr Tools won't be of help.
I tried all the usual stuff but the 2x2 took me on and off trying for a good several days before the a-ha moment came. It appeared that I didn't expand my thinking a bit further! Some careful analysis right at the beginning of how the wooden pieces can be possibly inserted into 2 flat layers of acrylic and how the puzzle will end up in the final state would yield dividends as you play along. And NO force at all is necessary!
Not an easy puzzle at all by any means and Mr Puzzle has rated the 2x2 at a difficulty level 9/10; ie very difficult, and I concur. At the time of this writing, the 2x2 is available from Mr Puzzle for A$38.50.