Whoa! This thread has gotten me concerned. Before this thing about the part # came up, I bought a Sapphire RX 580 Pulse 8GB card not thinking that a part # would mean anything. Looking at my card now, I see the part # is 299-1E387-000SA. Is Apple somehow cuing on part #s? If so, did I just shoot myself in the foot?
That's the manufacture part number, not the same part number we were talking about.
I think you have to dump the ROM to check that part number. And no matter what's on the box, label, card. Only the part number inside the VBIOS does matter anyway, better to check it.