The Magnetop was made by American Magnetop Corp. from Brooklyn, New York:
For completeness, let's mention other very similar magnetops:
Groovy Grabber from Aurora Plastics Corp., West Hempstead, New York.
Obviously, one is a copy of the other and being both from New York state I would suspect that they were business related: a split? a license? buy out?
The American Magnetop Corp. is a specific company around this top while Aurora Plastics sounds more generic. One posibility is that the American Magnetop is a spinoff of Aurora. On the other hand, the special starter would suggest that the Aurora top was a later product.
There is a Canadian version, by Peter Austin, that most likely was licensed or re-branded:
And then there is a more recent (circa 2000) Australian remake, the Moose Magnetic Top (there were three versions):
The Moose claimed over 10,000 RPM, but I doubt anybody can spin that fast a regular throw top.