Combined circuit breaker and RCD. In science language it is named "differential residual current circuit interrupter". Used in small fuse boxes, where are no place for installing circuit breaker and RCD separately.
<a href="//commons.wikimedia.org/wiki/User:Dmitry_G" title="User:Dmitry G">Dmitry G</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>