I would think there's:
the major labels
The large independent labels (Motown / Brunswick / Chess / Scepter / I am not sure of all the labels that would qualify, we could debate, Motown probably needs to be treated separately)
the bigger local independent labels (I am thinking labels like Arctic & Phil-la of Soul since I am near Philadelphia, but others that are similar)
the mom & pop / local labels with a handful of releases (I like the thought of a group or artist recording in the back or basement of a hair salon, which I read some where)
private press I am not sure about, would need some examples (unless you mean the package deals that some studios had where paying for the session would also get the artist a 45 on the studio's label, like my neighbor's brothers band)