There really is no way to tell them apart, even if you hold them in your hand - unless you turn them on that is. All of these lasers use the same cases. There are slight differences between series of cases produced, but those are not related to what's inside at all.
Also, a burning performance test is likely to be of little use. Things like cutting tape, popping balloons or lighting matches are all very dependent on power -density-, not just power. This means that, for example, lighting a match with a thick 200 mW beam is more difficult than with a thin 100 mW beam.
You need a power meter to tell for certain, or a laser of know power for visual comparison.. though the latter is by no means accurate beyond 'that one is brighter'.