thanks to all for responses. I,ll try to make myself clearer. Suppose I have 10 young head vic pennies of the same date and considered to be uncirculated and genuine. How likely is it that I will find ALL to be exactly 18.8G. If not what would be an acceptable "drift" before suspicions are aroused, ?1 decimal point or a fraction of 2 decimal points. I note the advice to use my eyes first but that could take years !!