Transforming into Sailor Moon
Act 1 Usagi - Sailor Moon (manga and reboot)
Manga and Anime
It was given to Usagi by Luna in episode 1 of the anime and Act 1 of the manga and crystal. Luna bribed her into transforming into Sailor Moon (tricked her in the manga and Crystal) in order to prove to Usagi that she had a destiny as a Sailor Guardian. Once she obtained it, Usagi began wearing the brooch in the center of the bow on the front of her school uniform when she was in civilian form.
Appearance in Sailor Moon Crystal
It is a round golden brooch with a crescent moon as a decoration and a gold star in the middle with four smaller round circles, one on each quarter, that represents each of the Inner Senshi that fight along side her; Red for Sailor Mars, Blue for Sailor Mercury, Green for Sailor Jupiter and Orange for Sailor Venus.