Здравствуйте товарищ милливольтметр! https://www.ebay.co.uk/itm/175033826065
Oohh that's a
special one, it says "Millivoltmeter". They usually say "Voltmeter", regarding of features, number of digits etc.
The seller has thankfully provided a high res shot of the schematics, now we can see, it's an AC-Millivoltmeter:
And look at that glory!
Fet input, mystery ic, opamp, transistor amplifier - it's even powered by a self-oscillating switch mode supply
No expense spared on that one!
In the bottom left of the display we can see some of the specs "0.1mV-300V 2.5% 20Hz-1MHz B3-55A"
2.5% is a bit of a bummer, but I'll guess there is a good chance it is still in spec...