Typically indicates the originator of the design, sometimes the particular devision of that company.
LM = National Semiconductor monolithic division
TL = Texas Instruments Linear division
NJM = New Japan Radio
RC = Raytheon
AS = Alfa Rpar
NE = Signetics
LF = National Semiconductor fet division
BA = I think Fagor was the originator of this prefix (a nod to their origins in Basque?)? Lots of buying and selling of divisions, so a wide number of companies have "inhereted" the prefix.
OPA = Burr Brown
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