A picture of the PCB would certainly give more information. I could make a guess of what generation of nvidia core it's using based on it's size, I could tell if it does indeed have 4gb of GDDR5. I could compare it to other nvidia cards and make a guess as to what it is. A GPU-Z screenshot would also be helpful.
What is not giving me any information is those numbers you provided. If the card is fake they are likely just arbitrary numbers that don't mean anything, I cant find anything on those numbers.
EDIT: If GPU-Z says its a GT 450, it is probably a GT 450.