You are absolutely right about everything. I think I understand better where you are coming from.
I agree that no one should ever trust anyone claiming brand new (unopened) and therefore you should always verify all documentation, and check everything yourself.
But that’s trust, and it is irrelevant to the second concern, which is what is second-hand and what is brand new. Second-hand implies it’s been owned by someone, there is no question about the meaning. This system was never owned by anyone and is straight from an official retailer (never unboxed), it was simply customised and built according to a specification by one of our client. The box has simply been delivered to our offices, left in our warehouse and is being re-sold by us. Re-sold does not mean that suddenly the parts are second-hand. It’s packaged officialy, just like Amazon (in your example). The only issue here (which I agree with you) is trust, and I believe I have enough documentation for anyone interested to prove this, and they are more than welcome to make their own judgement.
I hope this clarifies my initial post a bit more. No parts are being sold, but a ready to use system from a well respected retailer in the UK.