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).
{{Information |Description={{en|1=''Isoetes tegetiformans'', on granite outcrop in eastern half of Georgia Piedmont }} |Source=[http://www.fws.gov/athens/endangered/teplants.html US Fish & Wildlife Service] |Author=Anon |Date=Undated |Permission={{PD-USGo
File usage
The following pages on the English Wikipedia use this file (pages on other projects are not listed):