2023-01 update: I slightly modified the model and increased the hole through the skull to 3mm which should fit thicker strings/ nylon/ wire - this worked for what I needed on my end. I hope others can make use of this modification too. I added an extra small-sized skull. I've listed the sizes by height:

L = 52mm height M = 42mm height S = 32mm height XS = 24mm height

I think this is the best skull model here on Thingiverse. I had no issues with printing the original model upright without supports. I created various sizes with a small hole in the middle to use as a bead for jewelry-making, etc.

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