This is meant to be a general question - I'm not asking about any specific breaker. More of a practical methodology question.
Some breakers are clearly labelled as to whether or not they accept a double tap (two wires under one screw / clamp).
But if there are no markings or they are illegible, which seems to be common with older breakers I have seen, is it likely to be acceptable to assume a double tap is or is not okay based on the shape of the terminal clamp?
In this example there are clearly two 'slots' where the wires are meant to go:
Would seeing such a clamp (or similar) guarantee that this is OK to do?