when i fist installed a card i ran super position benchmark. this recognised the card as engineers sample.
when the item was sent back (a day after i recieved it) it was in its orrginal packaging completely. all i had done was install the card, run benchmark and then sent it back after it started to fault.
https://ibb.co/rGT9tRp
link to screenshot of sample
super position benchmark has nothing to do with it and could be reading the bios wrong or the bios is an older bios or the program is not updated to recognise the card correctly.
You said that OCUK said there is no serial number on the card and a sticker that states engineering sample on it where the sticker for the serial number is normally.. from what I understand .
Or did you take off the sticker at any point with the serial number on it and if you did, did you keep it and stuck it say on the box or manual ? Anyways once you remove these stickers what they leave behind is a mess that says void void.. So by removing the sticker which I don't understand why you would do that you have basically voided your warranty too.
Do you have any pictures of the card , did you take any of the front and back, as the back is where the sticker is normally for the serial number and warranty void stickers on some screw heads etc.