Sheer probability would predict 99% odds of Chinese manufacture, despite where the seller is located. But that is not actual proof. Why not ask them? As far as not being labeled PRC, tons of counterfeit goods arrive in US ports every day with missing or deceptive labeling. And with an item selling in very low volumes like the one in question, it would fly under the radar anyway.
But you never know - maybe the Chinese subcontracted it to a third world country with even cheaper labor, like Texas.