Using coins for scale is discouraged as it will require people unfamiliar with them to look up the dimensions or guess, both of which defeat the purpose of the object in the first place. Coins can also reinforce a geographical bias, and some coins' designs are copyrighted.
Ideally, a photograph should include a ruler with the subject (example) or an added scale marking.
SI ("metric") units are the most commonly used worldwide (see meter and centimeter).
Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster). [1]
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Ја, творац овог дела, предајем га у јавно власништво. Ово се односи на цео свет. У неким земљама, ово није законски могуће; у том случају: Ја, творац овог дела дозвољавам свакоме да користи ово дело за било коју намену, без било каквих услова, осим услова које намеће закон.
{{Information |Description={{en|1=Heavy mineral layers (dark) in a quartz beach sand (Chennai, India).}} |Source=Original photograph |Author=Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster). |Date=May 2008 |Permission= |o