Italian road sign of the beginning of 1900 (1907): slow down.
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)