Questions about HTC One M9

No, the device cannot be opened by the end user either. It only has slots on the side for the SIM and SD card.

Someone probably returned it, digitec checked that everything was as it should be and found it to be good. If you are referring to HTC One M9 (5", 32GB, 20MP, Silver on Gold), you can assume that the phone looks like new, but the seal on the packaging is broken and the USB cable is no longer welded to the original. In short: the product is as good as new and you will (almost certainly) not notice any difference. See also https://de.wikipedia.org/wiki/Refurbishing