MAC of br-lan and wan interface is not matching the real hardware address (Archer C5 v2)

Yes! I have several Routers around to test, but not your model:
Please try to run (replace 80091905 with your Pin)

cat /dev/mtd0 | grep 80091905
cat /dev/mtd1 | grep 80091905
cat /dev/mtd2 | grep 80091905
cat /dev/mtd3 | grep 80091905
cat /dev/mtd4 | grep 80091905
cat /dev/mtd5 | grep 80091905
cat /dev/mtd6 | grep 80091905

try /dev/mtd0ro instead or /dev/mtdblock0 if /dev/mtd0 if you dont found anything

info here: How to read TP-Link factory wireless pin from flash - art

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