I think its more direct that when you get a specified wire, you measure it with the most simple easy tool to use, unless its 600 strand.
you strip 1cm of wire. count how many strands. then measure one with a micrometer.
Thats the only way you will find it can be done accurately in a normal shop.
ALot of the people here facing fake wire problems (i.e. electricians) don't have measurement microscopes or accurate scales or even kelvin. A micrometer is something that is ubiquitous.
Here is a real situation: you routed a solar cable on the roof and got second thoughts
I am realistic. Have you ever dealt with installed wiring before? Some one leaves and your left with 8 inches sticking out of a wall, barely enough to get 1 rewiring out of it.
If you actually followed the fake wire problems on the forum, you would see how the big trouble actually starts.