Really enjoyed building this, and am using it for a small surprise Xmas gift. I only had a couple of issues with the build: (1) Step 4 in the assembly instructions confounded me a bit until I found a YouTube video -- it wasn't clear to me how the coins had to be related to the dials and I was scared I would do it wrong; and (2) in my build, the symbol wheels don't spin as freely as they should, and it's easy to tell (by feel) how to set them to free the compartment. In hindsight I think there was a little extra support material left in the discs [where the cams are inserted] that keep them from aligning well. I ended up using a grey ABS for the core pieces (mostly due to a lack of black PETG, which I used for all the cams and the edge frames) and did the rest in a mix of PLA Metal Gold, PLA Metal Blue, and PLA Translucent Blue. The translucent looks really nice over the grey material of the core box.