Replacement box bracket for Venetian blinds. For a 25mm high by 26mm deep box section at the top of the blind.
Made in onshape: https://cad.onshape.com/documents/234d0437119616be1931f246/w/deafba2dd202c166dde8cd80/e/2acdc82fdc118b349d203a79?renderMode=0&uiState=62f7dadfddf87e64bdd5def8
The author hasn't provided the model origin yet.