This is a Qing dynasty coin called a Qian Long Tong Bao. Emperor Qian Long reigned from 1736-1796. This coin was made in the Aksu mint in western China and which was famous for its claylike red colored coins. I love the Manchu script on the reverse of this coin.
<p>24-5mmx1mm
</p>
乾隆通宝　背阿十
Dr. Luke Shepherd Roberts
Attribution
<ul><li><a rel="nofollow" class="external text" href="http://roberts.faculty.history.ucsb.edu/coins/Chinesecoins.html">Chinese Cash Coins</a> (<a rel="nofollow" class="external text" href="https://www.ucsb.edu/">University of California at Santa Barbara</a>).</li></ul>