Question Rx 580 - Is it Fake?

Mar 11, 2020
Current System:
AMD 2600x
Asrock b450 steel legend
Ballistix 2x8gb 3200 RGB
Gamemax 550w fully modular PSU
Rx 580
Seagate barracuda 1tb
Kingston a400 m.2
Gamemax crusader Case

I have upgraded my GPU to a 5600xt and am going to sell my RX 580 which I bought on eBay from a man who was selling 5 others after using them for mining for 3 months, I only realized this after purchase a few months later. I did not have a monitor yet so I used my parent's tv to see if it would boot and it did. Then when I got my peripherals it would not boot to the monitor, so used the tv and downloaded the correct drivers and windows which then worked perfectly for the monitor. when I upgrade the system to my current one but still using the same graphics card I had to do the same thing and was still not able to access my bios from a monitor. i upgraded my graphics card and I can now access the bios from the same monitor.

Trying to now sell the graphics card I thought I had an outdated RX 580 bios so I upgraded it and it would no longer post so used the bios switch to switch bios and then it posted, so I want to know if the bios update caused the flashed bios if it was fake to not work, then the card would be fake and if I would be able to sell it still and to find out what card it is?