To what is this capacitor connected? (OP-amp)
Usually external compensation is a series R-C. Some very old op-amps (eg. LM709) had separate input and output compensation. 



For an LM741 maybe they are putting a capacitor across the offset null terminals. I can't say as I've seen that recommended before. Or maybe the schematic was originally drawn for another kind of op-amp that required external compensation.