Andriy Bruns' barrel puzzle is a pleasure to hold. It's an incredibly well machined piece of art, fun conversation piece and small enough to be a great fidget distraction when on the phone or doing other work. Everything is well polished and finished. It arrives assembled and unsolved and to the naked eye, the cuts are made so precise it's hard to see the initial seam.
I would rate this multi-stage take apart puzzle as perhaps a level 3-4 difficulty level simply because it provides constant sound and tactile feedback to actively assist in the solve through each step vs. something like Felix Ure's Titan which is clearly a level 10 and frustratingly obtuse. Where the titan requires hours upon hours of brute force testing to blindly open, the barrel is IMHO actually a more fun true incremental puzzle. You can see results and have enough visual/sound/tactile information to make educated guesses towards the next stage. This puzzle would be well suited as a great introduction to take apart metal puzzles for young teens. Opening the puzzle does reveal about 10 unique smaller parts that come out so I would not recommend for younger children. The 'prize' of a uniquely crafted coin is a nice extra touch giving you a nice keepsake for reaching the goal. The coin could be replaced with a different item around the size of a nickel. A krugerrand gold coin perhaps?
Re-assembly / Reset of the puzzle is a fun second goal.
While the puzzle can be solved in under an hour, the beauty of the piece and easy one-handed holding provides a lot of repetitive enjoyment and fidget value.
I also want to call out that this puzzle was hand crafted in Andry's personal basement workshop, in the Ukraine. I'm more than happy support Andry during what can only be described as very difficult and sad time for him and his family.