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<p>[QUOTE=&quot;desertgem, post: 1778263, member: 15199&quot;]How can a person use it to decide if a coin/round/bar&nbsp; is good or not if they do not have a fake on to compare it with?&nbsp; A positive control as well as a negative control is necessary when one is doing an unfamiliar test of any unknown.[/QUOTE]</p><p><br /></p>

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