Postcards often depict the regiment number in ornate form. Often, this depiction is like a plan for a cap badge. I am almost certain of this sometimes, even though no information other than the drawing is available about that badge.
At other times, however, the depiction is not as convincing as it is here on the postcard of the 13th Landwehr Regiment. Undoubtedly, the depiction is like a badge, but there is no other decoration besides the numbering of the regiment, a sign referring to the regiment. As a comparison, of course, I also present the cap badge of the regiment here. Nor is it too imaginative, but at least the usual attributes are on it: the portrait of the ruler and the imperial crown. But there were some simpler badges that showed nothing but the inscription or just a number. So, even here, it cannot be ruled out that we see the design of a badge on the postcard.
The 13th Landwehr Regiment was organized in the Sudetenland, so its staff consisted mostly of native German speakers. Next to them were Czechs and Moravians in the regiment. The card was just sent home by a Czech-speaking soldier to his relatives in Troppau (today Opava). The command of the regiment was in Olmütz (today Olomouc).