Italian road sign of the beginning of 1900 (1907): dangerous bend. Note that the name of the donor of the road sign is not clear (since the poor quality of original image) but it is likely to be an automobile club.
Rivista mensile del Touring Club Italiano, N. 4, aprile 1907, A. XIII, pag. 111 (https://www.digitouring.it/wp-content/themes/touring-theme/pdfjs/web/viewer.html?file=https://www.digitouring.it/cataloga/media/digitouring/images/0/0/25338_ca_object_representations_media_72_original.pdf)
Touring Club Italiano (the vector file made by Civitas13)