That's puzzling, if its the best charger ever made and they went out of business?
Reverse engineering is a field on its own, and you need a pro to decipher it as chips get denser.
20 year old design could be deciphered by design familar EE, with good likelihood of success, but
its a lot of work.
As edonork said, a photo helps, because the layout can estimate analog from digital logic. Even if the chips have been sanded, if you use a microscope you may still find traces of the etched numbers.
The formal process is you have to trace all the components and create a schematic. Label everything you can label and identify. With a DMM, check the output of each pin as the device is functioning and get voltage levels. Label all the voltage levels on each line. Now check the same with a scope and identify the type of signal on each line.
From the signals on each pin, you can approximate what type of chip it was: op amp, clock, logic gate etc.,
Now which model op amp, clock, logic gate etc., it is, become even more difficult, but at least you aren't in the dark! Luckily, you can substitute a superior chip for an inferior one, so for example, if you find a 741 op amp, anything above it will work, assuming it has the same pin outs.
This info generally helps in troubleshooting and repairing a damaged device, but to clone it, you have to I.D. all the components. This becomes more difficult if there are any custom ICs or memory chips with firmware, as then you need to extract the firmware and reverse engineer that too.