it's a Liechtenstein road sign, described in http://www.gesetze.li/get_pdf.jsp?PDF=1980065.pdf
CH-Hinweissignal-Ortsbeginn_auf_Hauptstrassen.svg
CH-Hinweissignal-Ortsbeginn_auf_Hauptstrassen.svg: Bundesamt für Strassen (ASTRA)
derivative work: Filzstift (talk)