Jerry G. wrote:
All these series of devices, and many more types are Japanese numbers.
Other companies buy them up for productions, and have the manufactures
screen their names on them (the name of the buyer), to say what they
want. In many instances they also change the numbers to their own house
numbers, if they want the exclusive spare parts sales. This way the
servicer cannot have any spec listing, because the part is a house
number.

With popular type numbers, you may find many manufactures having the
same part number type listed. But, maybe only one or two manufactures
originally made the part.

Some companies buy the bare chips and package them in their own
packages. Some chips are made in fab plants in one country such as the
U.S. and the chips are shipped to an assembly 'maquiladora' plant in
another country, sometimes halfway around the world, or perhaps Mexico.
So it's hard to say what mfgr or what company made what.

And then we get into what chip is used. In National and TI transistors,
(yeah, they're not doing those anymore) the manual tells what chip is
used for what transistor. Some chips are used for many transistors, the
diff between them sometimes being only the testing and selection process.