there is no physical way of differentiating them aside from the part number.

It's theoretically possible to differentiate them electrically by applying voltages and measuring voltages and currents, but the number of possibilities is so huge, it would take you years to test just one part.

If the parts are on a PC board with reference designators, such as IC27, you can get the schematics and bills of material for the PC board and look up the part there, but getting that information may well be impossible. Most companies do not give out that info.

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