Have a good collection from Argentina but stopped collecting around 2006 .Found a bunch of stamps that seem ok with an added "OCA simple " added . Also correo privado .. What are these ? Thanks . They are not in my 2013 Scotts .
Those are both private postal corporations that run in Argentina. Many countries have monopoly postal services, that are either run by the government or are private or semi-private corporations, but other countries permit private companies to run their own postal services and compete directly with the government post.
Scott doesn't list stamps issued by modern private posts, unless they have a monopoly on postal delivery. I consider that an unfortunate editorial policy (only one of many though).