What It Changes in Pop-out Clocks

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Precisely one thing, and only in one place.

Where the clock is	What you see
In an item frame	The new raised 3D clock
In your hand	Vanilla clock, unchanged
In the hotbar or a chest	Vanilla clock, unchanged
Dropped on the ground	Vanilla clock, unchanged

That split is deliberate. The pack's item model definition selects on the display context and swaps in the 3D model only for the one an item frame uses, falling back to the vanilla model everywhere else. Nothing about the item itself changes: same crafting recipe, same behaviour, same stack.