please help about recalibrate fake fluke 8020

[unicornio]

hi, there,

i need some info to recalibrate this multimeter. is a 8020 copied multimetar from Lutron, Taiwan. it have more than 30 years and yet work fine, but i want to recalibrate it for now.

it are not cheap, but it demonstrate that are well build and is a very durable unit.

I discovered a secret position in which to measure its own supply voltage and I got a table with the references.

if anyone has any multimeter like this, even with another brand, maybe if you have any information about the use of different setpoints, we would be very grateful ... the fluke 8020 was a nicely device that caused sensation with its new design , very good accuracy, ergonomic  and robustness, so it was much copied by many oriental manufacturers.