The Hyperboloid Burr puzzle from Two Brass Monkeys is a 6/7 piece puzzle with different solutions for each.
Made from seven identical brass hyperboloid pieces.
Originally designed by Oskar van Deventer and made in a wooden version. Initially a six piece puzzle, it was discovered while working on the original a seven piece solution also existed. With permission Two Brass Monkeys have recreated it in brass.
The six piece version assembles well but if picked up by a single piece will fall apart. The seven piece solution completes with a satisfying click and holds together well.
These were precision CNC milled in the UK. The tolerances for this puzzle were critical, a 0.03mm out and the seven piece solution does not assemble.
A really nice looking puzzle this comes disassembled and does not include the solution.