Flexible licenses: Feel free to choose one of the free licenses stated below. Usage is free of charge, but this image is not in the public domain. If you would like special permission to use, or license this image please contact me to negotiate terms.
Using online: For an example of reusing my images look at the right. It shows the name and a link to the used license.
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).