Stock commingling means that you may buy a product that's sold and shipped by Amazon and still get some other seller's counterfeit. That seller simply claims to

Stock commingling means that you may buy a product that's sold and shipped by Amazon and still get some other seller's counterfeit. That seller simply claims to sell the same product as Amazon, with the same product code, and places it into an Amazon warehouse. Amazon will ship from the place closest to you so they might just ship what they think is the correct item from another seller's stock even if it's actually a counterfeit, and do the clearing later. They later assign one genuine item from the Amazon stock in another warehouse to the seller's stock. As a buyer you have no control over this and Amazon does their best to be opaque and not allow buyers to publicly flag issues beyond a return and refund because it would reflect poorly on Amazon's image and make them look like peddlers of cheap knockoffs.