This is a very high gain differential amplifier with few stages that does not oscillate with negative feedback. It also has 0V offset voltage assuming it was made perfectly and in a perfect environment.
Edit: Upon further measurements I find that the gain is actually 5.5mA/uV (for every 1uV increase in difference between the two inputs, it outputs an additional 5.5mA) and that the offset voltage between the inputs is 0.1uV (almost exactly).
