While searching a capitulation site in Northern Norway this summer, where units from I.R 193 capitulated after having withdrawn from the fronts around Kirkenes-Murmansk, I found three brass tubes which was used by messenger dogs.
They wore it around their neck and carried messages between i.e the frontline and HQ. The message was written on paper, the tube was unscrewed in one end and the message scrolled up and the tube was closed.