How many string makers are there?

[Will]

I remember hearing many many years ago from a fellow who worked for Marshall that there were only a few string-making machines in the world (he said 6), thus most companies were just branding something produced by a third party. Is that true and, if so, does anyone have a guess as to how many different makers there are?

I know all nylon and flouro-carbon treble strings are fishing line, and that many makers only make the wound strings (plains are just wire stock with a bead tied on). Anyone have any other dirty details?