Another ruler/straightedge made in Germany by A.W. Faber Castell. This one is about 12 inches long, which makes me wonder for which market it may have been made. A quick search revealed that Germany’s metrication began in 1872, but since this ruler has “Castell” in the company name, its earliest possible date of manufacture would be 1905.
A more likely explanation: 12 inches is nearly 30.5 centimeters, so it may very well be that this is a metric straightedge to begin with.
Like the ruler from a previous post, the edges are reinforced by strips of brass, inserted at a 45˚ angle.
And like the hexagonal ruler, this one still works too:
Thanks to Michael for the post-war Castell 9000.