Experimental comparison of electrostatic repulsion for positive and negative conductors

Coulomb's law predicts that two charges of the same sign repel and that two otherwise equivalent charges ($+Q,+Q$ and $-Q,-Q$) should therefore produce the same repulsive force.

Physically, the two cases are rather different in an ordinary conductor. Negative charging means adding electrons, whereas positive charging means removing electrons.

This made me wonder whether the two cases have actually been compared experimentally.

Are there experiments in which the mechanical repulsion between two positively charged conductors has been measured and quantitatively compared with the repulsion between two otherwise equivalent negatively charged conductors?

In particular, I would be interested in experiments where the positive charge is produced by removing electrons, for example by photoemission, and where the charge magnitude is established independently of the force measurement.

I am mainly looking for experimental references. I would be grateful for pointers to either classic or modern experiments.