Tag 'historic = optical_telegraph'

Value histogram for key 'image'

• 1: https://commons.wikimedia.org/wiki/File:TelegrafenstationPotsdam.JPG
• 1: https://commons.wikimedia.org/wiki/File:Prussian-optical-telegraph.jpg
• 1: https://commons.wikimedia.org/wiki/File:Station-1-pruss-teleg.jpg