I have read the datasheet a few times and find it a quite complicated device. I think is used to regulate the load when charging the battery, but I’m not very sure of that.
From the datasheet which was first published in January 1983 and revised March 2017, a 34 year old active document (And active part) that has to be some sort of record!
The die size is 2.08 mm x 1.9 mm (3.95 mm2) another single metal Bipolar process.
From this diagram in the datasheet I was able to identify the pins. The output transistors are obvious and I can see the error amplifiers and some of the other functional blocks