I had one. Sold it bc it just took up so much damn space, but it was a great machine. Loved opening up the side panel - the interior layout had the designer’s fingerprints all over it, just so orderly and mechanically beautiful. To the best of my knowledge it was bent-up aluminum, with a significant amount of post-processing including (guessing) substantial caustic etching to remove any tooling marks. The housing was sturdy and well finished, but it was the custom perforated grill that is a real design and engineering feat. There is so much material taken away to provide a high percentage of open-area, yet the dots line up well, they were all perfect, and the material was thick as well which one would think makes perf difficult…not for Apple.
The new flagship desktop product is another tour de force but for other reasons.