I'm not really sure about  Gulden as it is a currency that focusses itself nationally (The Netherlands). I'm not sure why retailers would not use Bitcoin or ethereum instead. It's cool to own some Guldens again though. They sure do have a great team working behind it though and it could become very succesfull in local stores. I definitely think it won't flop but I wouldn't expect this to be some crazy investment where you can see huge returns.