one difficulty that this seller's items causes for me is that he "specializes" in hammered bronze or copper.
Genuine VOC coins had very simple designs and were often minted to a "rough & ready" standard - perfect for 21st century counterfeiting. Pitted surfaces are the norm. Chemical aging is inexpensive.
I did buy some Batavian duits off another Javan dealer, who was reasonable for postage. I think I got three for $8, including postage. I won't know if they're duds until I meet an expert, but at least I didn't pay much.
Saruma, not that it matters in terms of the point under discussion, but Java was British-occupied from about 1811 to 1824.
Peter in Oz