In The Annunciation, by Baldovinetti, who is in it?

The Annunciation is, in Christianity, the revelation to Mary, the mother of Jesus by the angel Gabriel that she would conceive a child to be born the Son of God. Some Christian churches celebrate this event, which happened in "the sixth month" (Luke 1:26), with the Feast of Annunciation on 25 March, which as the Incarnation is nine months before Christmas.