Besides the technical features that I've already pointed to, look at the engraving. I can't find a single design element of the engraving that both guns share. Hard to explain if both guns supposedly came out of the same shop in Vienna.
Just because this gun has elaborate engraving work, doesn't mean that it couldn't be a fake. Also, the engraving work on this current gun looks second rate compared to the one seen of Hermann Historica.
Fakery exists. It's existed as long as there has been interest in collecting firearms. Ground zero in the world of fakery is merry ol' London. There have been antique arms dealers in London who strongly believe in always delivering what the customer wants. Always. Can't find a beautiful Austrian Contriner or Austrian Army Girandoni? No problem. They would make one. Fakery is a big part of antique arms collecting. And that's exactly what I think we're looking at: a very elaborate fake.