id small pretty letter opener

[vitorvt]

I finally found the forum I was looking for. If it's not here, then I don't know...
I'm Vitor T., I'm in Lisbon, Portugal, and for a few months now I've been trying to identify this small, beautiful letter opener that I inherited from my father.

I've already received the opinion of some experts, namely:
it's not Spanish,
it's from South America,
and the latest, which also seems most likely to me, is that it's a hunting knife "Jagdknicker", probably from eastern Germany or possibly western Central Europe, neo-Gothic style, 19th century around 1850-1860. I would like to confirm this identification.

There are a few issues. The mark or signature Jst. remains unidentified. Another is that after looking at thousands of images of knives and swords on the internet, I have yet to find others with the geometric elements of brass on the handle, or the composition and design of the handle, the figures on the blade, the shape of the blade, or a similar sheath.

Please help.
Thank you.