If you modeled it exactly the same way to the point where someone could look at both models in wireframe and not be able to tell them apart - which is very unlikely, speaking as a pretty experienced modeler - then it could come back at you.  Otherwise, it's not like a model of a current military helmet is something the modeler could say they originated.  The designer of the actual helmet, maybe.  If you design your own stuff, this will never be a problem.

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