I’m no electricityologist, but wouldn’t that make half your circuits 240V and the other half deadly 0V?

I imagine this varies a lot on which country you’re in. In the US, coins seem to be mostly toleranced at around 3-5%, but you could probably get away with a large number of coins in good condition from different years.

I think you’re a bit off track. scale accuracy has been a subject of careful scrutiny for millenia. You absolutely have to use the right tool for the job. A kitchen scale is not the right tool for the job. It would be like complaining that you can’t take your car’s lug nuts off with a pipe wrench.