The code is a reference for the country or continent it was sent to. 584 was the US market and if you go down a bit the Euro XSC was 1E1 and French XSC was 1h1.
Some times the code was used as the ID Number prefix. The US 78E /79F Standards, used the 2F0 code as the prefix as well, but the 78SE/79SF Specials had a 2M0 code and used 2F0 as the prefix.
Code has no real meaning unless it is used in your 17 digit frame id tag