Copyright only applies to created works (stories, scripts, music, video, pictures, graphics, etc.), not to manufactured items. (And applies from the moment of creation. Formal registration of it is not required.)

A Patent is what restricts others from duplicating a physical object. And often covers modifications to and derivations of that item.

If this shows any sign of becoming more than a hobby, you'd be well advised to talk to people that know the laws before anyone comes knocking.

CTB ("Covereth Thy Backside").