"Money of account" is the American term, and it's in both my American Heritage and the Grolier's CD, so it must be a relatively common term. It means the currency in which accounts are kept, which may or may not coincide with the actual currency in use.
I would guess "society" is in this case the Italian word to describe a corporation; "S. A." (anonymous society?) is used in some Latin languages to denote such. "Company" refers to an organization, but not to it's legal status, so individual enterprises and partnerships may use "company", but in the US, "Inc." refers to the fact it is organized as a stock company, with unknown ownership and liability for debts limited to the assets of the enterprise, not extending to the personal assets of the owners (as would be true in partnerships or individual enterprises). At one time, virtually all stock brokerages were partnerships, but I believe most of them are now corporations.
[This message has been edited by Pete G. (edited 05-27-2001).]