“The seller is “Military Base” not Amazon directly.”
If you have ever searched on Amazon, some items are sold directly by the company, and some are “FSBA” (for sale by Amazon) - i.e. they are actually sold by 3rd parties, but Amazon gets a cut for exposing it to millions of people. “Military Base” is likely just the name of a company (or the scam set up by BATF) - Amazon controls the naming of non-Amazon sellers in any way.