You may have seen on customers unboxing videos some boxes with a grey sticker on one side of the box. Note that new boxes do not have this sticker on.
Ledger doesn't attach any tamper proof seal on its boxes anymore as it is not useful. We used to put this grey sticker during a few months, long time ago, but it was a standard sticker, not a seal at all.
In your box, there is a card with a "Did you notice" title, explaining it. If for some reason you don't have it anymore, you can read this blog post to understand why the best practice is not a seal - easy to fake or replace - but attestation to prove the authenticity of your device.
As you must initialize your device before using it, your device will be set up with a security passphrase that only you will know. Make sure to "create a new wallet" when you configure your new device.
Also, your device will be checked by the Ledger application on which you will connect while using the device:
If your device is recognized, it is a genuine Ledger product
If your device is not recognized, it can be due to a simple failure (see this guide)