Is it possible to check if the case was opened previously?

You can tell from the screws. A computer that has been opened will probably have scratches by the scrfew holes, scratches on the screws or they could be stripped. Missing screws is a hint, too.

Another way is look for scratches by the holes. You can tell a screwdriver scratch from a table scratch easily in many cases. Also, check the Threadlock. Busted Threadlock can be a symptom but it can also be worn out, too. I would check into this, too.

Also, look at the screw torque. If it comes out easily then it was opened. If not, it probably wasn't.

Non Apple parts are a dead giveaway.

However, these may or may not show based on the experience of the person working on the laptops. Some people are better then others at it. Idiots lose screws and strip them(however, experts can too). Experts know how to avoid all of this, so it's far harder to tell if they know what they're doing.

Rush jobs are obvious, too.

As a smaller tech and not in a position like Apple I don't toss third party parts. If they're bad I usually give them back. If they work they stay. I don't see what the big deal of this is. Liability seems like an excuse to me. If someone has a non OEM hard drive I do take notes, though. That's the extent of it.

yes

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