Ways of testing if a laser works?

I have two lasers (both KHS-400B) and I know that one works and one doesn't, problem is I don't know which is which! Does anyone know a way of testing them without putting them in a PS2? I also know one is older than the other, anyone know which with these figures? One has 09112KE1, D573 & C651 on the side (on a pink label) and the other has 02Y00KE1, D544 & C649 on a green label.

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