From the article: "The rebel Congress has passed a law, authorizing the issue of five millions of dollars in copper coins, of the denominations of five, ten and twenty-five cents. "
The REBEL congress!! :D
This is what sounded old to me: "very gross wrong upon the people, in thus repudiating its own stamps".
Also "wrong upon" has become rarer than "wrong against" or "wrong to", "the people" has become rarer in this context than "the public" or has different connotations, and "thus" has become somewhat archaic in senses other than 'hence, consequently'.
Maybe there are even other things here that I've overlooked.
Notably, Portuguese had multiple spelling reforms since 1862, while English has never had any (which is not to say that English spelling has never changed, but there have never been effective government decisions to change it abruptly). That probably makes Portuguese from that era look more visually distinct from contemporary Portuguese. For example, the enacting clause of the Lei Áurea, 26 years later than this text, says
A Princeza Imperial Regente em Nome de Sua Magestade o Imperador o Senhor D. Pedro II, Faz saber a todos os subditos do Imperio que a Assembléa Geral Decretou e Ella sanccionou a Lei seguinte
(differences from current Portuguese orthography italicized)
By contrast, there are approximately no differences in spelling between this article and present-day standard English, but that doesn't mean that all of the vocabulary is used the same way. For the Portuguese, it's easy to be struck right away by the fact that words are no longer spelled the same way...
A random bit of trivia - the CSA never issued coins. There were two attempts - a cent and a half dollar - but neither made it past the "proof" stage: https://www.pcgs.com/News/Confederate-States-Of-America-Coin...