It is a "gaucho" knife, slightly different from the more traditional type, made by Zivi-Hercules in Brazil, that also manufacture the Mundial Brand kitchen cutlery.
"Gelodur" is their marking indicating that the blade underwent cryogenic heat treatment.
I'm not sure what "Platinox" exactly means.
I bought a very similar, if not identical knife at a flea market in Sao Paulo, about 10 years ago, because I wanted to rehandle it. I think that the current fair price is somewhat lower than US$ 120.00, in fact there is a very similar one for sale at "Mercado Livre", our version of inline auctions, at:
The asked price is about US$ 70.00 at the present exchange rate.
I hope this little bit helps.