You can't rely on any single seal or any single thing to make a judgement.
For eg., last year I ordered a ASUS laptop from Amazon (Cloudtail or Appario) and an Intel processor from Flipkart (RetailNet). Both got delivered on the same afternoon and both had the tamper proof seal broken. I was sad and angry to say the least. Then I noticed that the insides of the laptop are untouched, all the items are packed as they were in online unboxing videos, there were small fine carton dust inside the packaging that is often present in the new laptop. I checked everything, everything was as it should be other than the outer seal which was placed on the box.
Then I closely inspected the seals to see if there are any nail marks or anything similar around the corners or the seal, there were none. It felt as if the glue gave way and the seal just came off. I googled this and then I found out that sometimes when boxes are handled roughly (multiple falls or dunno), the seals might come off looking like that. I ordered the items in a remote town so maybe they were handled very roughly while transporting.
So yes, as
@singenaadam and
@gourav already told, look into all the things, veryfying serial number, watch multiple youtube unboxings and compare them with your product, etc.