Dr. Volker Latussek wrote about it:
“Dear Mr Coffin, when your HALF HOUR was published as a packer at Cubicdissection last year, I myself played with your basic idea of splitting a 3x3x3 into three penta-cubes and three tetra-cubes to add a cube-shaped box with six pieces to my FLOP SERIES. That doesn’t work with your HALF HOUR, but there is actually a similar set of six pieces that has nice movements in and out of the box. I wonder if I can call the puzzle COFFIN-FLOP? Pelikan will publish the puzzle. Do you have any requests for the wood types?

STC: After all these years, what a surprise. I never was very good with names. Often that was the hardest part. I have been so busy with other projects lately that puzzles are now in my past. But they were fun, especially dissections. No opinion on type of wood. I used whatever was available. Keep up the good work.”
Stewart Coffin (STC), Massachusetts, born 1930, 05/10/2024

The goal of the puzzle is to pack all the pieces completely inside the box.