An egg of Acromantis japonica, and 10 yen coin(Diameter  23.5mm)
<a href="//commons.wikimedia.org/wiki/User:Tarabagani" title="User:Tarabagani">Yasunori Koide</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>