Used GPU Problems

I've bought a used gigabyte 7970 ghz edition off ebay and have the feeling there's something wrong with the product. 

It's meant to have 1100 mhz GPU clock and 6000 mhz memory clock out of the box but GPU Tweat and Catalyst Control Centre and showing speeds of 100 0mhz and 5500 mhz.

I'm not sure what to do?

ghz=gigahertz=1000mhz core clock

So nothing is wrong with it, it's meant to have a stock core clock of 1000 mhz (1 Ghz) and 5500 mhz memory clock.

That's the box for the product and it clearly states a 1100 mhz core clock bump it up to 1100/6000 maybe?

I've got the feeling I've been sent a 7970 that isn't the GHz edition. 

Is there a way of finding out?

It has a boost clock of 1100Mhz and a base clock of 1000Mhz.

Pull the card out and look around it you will see a Dual BIOS switch click it the outher way if you whant it in 'boost mode'

Both show the same results :(

You got scammed hard! Haha no just kidding, check the GPU with GPU-Z, free downloadable utility, just google it, and it will tell you what card it is. Even if it is 7970 instead of 7970 ghz, doesn't matter just have to overclock yourself. 

I've tried overclocking to 1100/6000 but keep getting a black screen in games. 

Does this indicate a faulty card? Perhaps the reason the seller was selling in the first place?