MAGIKON Precision Steel Scale Calibration Weight, M2 Class (100g, Single)

This small and heavy enough to hold down a key on a keyboard?

What is the diameter and height of the weight?

Is this a class m1 or m2? title says m2, which has +/- 16 mg, but the body of the post says it is +/- 5 mg which is m1, that's a variance of 300%

Is there any lead in this?