The Lord Regent's Crest.
The Child Empress is a book found in Dishonored 2.
Transcript
[Excerpt from a Historical Series]
There was a definitive moment when people stopped calling Emily Kaldwin "the Child Empress." It came after an ambush by the "Regenters," an extremist group who wanted to return Dunwall to the authoritarianism of the Lord Regent's time.
On the way back to Dunwall Tower, Kaldwin's carriage was blocked between two gates, with her attackers firing pistols, and even throwing a grenade. With the Royal Protector too far away to be of service, the young Empress, only fourteen, found herself all alone in the carriage, save for her friend, Alexi Mayhew .
Kaldwin supporters are lucky that Mayhew was there, as she was brave enough to grab a grenade that had landed at their feet, throwing it back at the assailants and saving the Empress. When one of the men dropped down from the forward gate, it was Emily Kaldwin who yanked free a short railway brace and beat the man senseless with it. With the City Watch closing in, the two girls held their ground against the debris of the carriage until the situation was secure.
It is said that Emily Kaldwin refused to have the "Regenters" executed for their crimes, and this is hailed by many as her first adult decision as Empress.
Cited for her heroic actions, Alexi Mayhew was commissioned by the City Watch when she turned eighteen, and was later made Captain, by Emily Kaldwin herself.
Location
It can be found on the top floor of the Regenters' outpost in the Lower Aventa District during the mission The Clockwork Mansion.