Welcome to TPF! I have a Gustto Setela in caramel - I think it's a little bit older bag, one of the earlier ones made. The tag inside my bag does say "Designed in the USA" under the Gustto name, however, I think the newer bags only say Gustto.
It also seems that these bags vary from style to style - A Baca might only say Gustto inside, but a Setela might say Designed...USA. As well as the med Setela and the large (I think the med only says Gustto).
You'll also discover that the newer bags have yellow lining w/the black Gustto signature print, while older bags are just plain yellow.
If you're unsure about the authenticity of a handbag, you can mention the website, and we can probably tell you whether or not it's a legit site selling authentic bags. Sites like Active Endeavors, Revolve, ADASA, The Purse Store, JCMadison, Shop Bop, ShopTwigs, Pink Mascara - they all sell authentic bags. It's very possible that a Gustto on one of these sites might look a little different than one on another. It all depends which style the bag is, the color, and when it was released.
Hope this helps - Welcome again, hope to "see" ya around!!