haha, who else would try to pull this shit other than some guy from my goddamn country...
anyways, I assume you bought your card(or intend to) via njuškalo(croatia's craigslist)
that's the thing when buying stuff from craigslist, you have to realize you're getting(at best) a new/not used much or used product which comes cheaper than buying from an authorized seller/retailer for the price of not getting a warranty and possibly a product without included accessories you would get otherwise.
In other words, buying stuff from craigslist/ebay/etc. is a gamble and the question is can you afford that?
if you can't, then save up some more and buy cards from a retailer like most people do.
or accept a gamble but don't ever try to pull that thing...
people are not that stupid.
actually card's serial number provides some info such as manufacturer, date of production, type of gddr memory(i think)...
from zotac:
Warranty claims will be void if the user:
· Tampers, defaces, or removes any stickers containing product identification information such as model number, serial number, or part number.Rofl
They are brand new, unopened. Probably he have some ways to order them cheaper or smth, no idea. They are not fake or used 100% just no invoice and he probably dont want to print one to not connect himself or whatever.