"KAG Classic," later on known as Beta, is the original form of King Arthur's Gold, with the newer version known as "Alpha." Besides the fact that they are two separate games, they were still developed by the same developers (or at least we're past the first release of Beta and Alpha), and both have "sprites" (in-game images) made by "Geti." KAG Classic was finished (or rather become Classic) when build 591 was released.
KAG Classic notably has characters (Knights, Builders, and so forth) that are slightly slimmer then Alpha sprites, and have typically have brown outlines (#260D0D) instead of Alpha's practically black outline (#130D1D). Strangely enough, while all human characters (i.e. Archer) have both a male and female sprite, whose team-colors will be changed by the code depending on what team the character is on, and head will change depending on what the player and/or code selects, the Beta Migrant only appears as a male, sprited with a specific head (no head-choosing code) in green-colored clothes that are NOT changed by the code.