How one can detect if a Graphic Card's BIOS was flashed before?

I'm planning to buy a used Graphic card and I want to know whether the person using it had flashed the BIOS before, put a custom one and now that selling it just replaced the default BIOS again or not.

Solution 1:

Graphics cards do not keep a record of what they got flashed with or when so there is no way at all to say for absolute certain that it had been reflashed or what with. They could easily save the current VBIOS, reflash it with a different (potentially damaging) version, then reflash the original.

The only way you might be able to tell is if the VBIOS version does not match the known versions that generally come with that card. A list of VBIOS versions can be found at Techpowerup VGA BIOS Database so you can see what version have been seen on a particular card, and you can see what VBIOS you have using GPU-z. The problem is that this is not foolproof and it might be that if your VBIOS is not in the database for your card then it is still correct for that card, but has not been seen before.

Again, there is no foolproof way to know whether the card has been tampered with or otherwise damaged. If in doubt you should buy from reputable sources.