Discrimination of measurement contexts in quantum mechanics

We demonstrate that it is possible to discern the way that has been followed to measure a quantum observable that can be expressed in terms of different products of observables, whereas no such discrimination is possible by assigning predetermined values. Specifically we show how to distinguish different routes (contexts) to measure C=AB=A’B’, when C,A,B and C,A’,B’ commute with each other, but A and B do not commute with A’ and B’.