letter scale

The special feature of this letter scale is the base. The scale mechanism is known as a model Fertig of Philipp Jakob Maul from Hamburg in Germany. The Fertig patent DE228054 was granted in 1909 and was published in 1910. Elsewhere on this website there are other versions of Fertig letter scales, see for example this one with links to other Fertig scales.
The scale base is made by Erhard & Söhne from Schwäbisch Gmünd in Germany. The base has a root wood top layer with a beautiful brass pattern inlaid. The manufacturing technique is said to be protected in a world patent in 1904. World patents do not exist. The first so-called "world" patent via the PCT (= Patent Cooperation Treaty) is WO 00.0001 and dates from 1999. I have not yet seen a single patent describing the brass insertion technique in root wood of Erhard & Söhne. Who can help me?
The company Erhard & Söhne was founded in 1844. Around 1900 there were 3000 employees! Between 1900 and 1910, the company exported many of their particularly well-executed dollhouse products to America. Earlier I presented a fire gilt dollhouse letter scale made by Erhard & Söhne, see here.
An Erhard catalog sheet, found on the internet, shows four different letter scales placed side by side, see the bottom of this page. On the left a Fertig model with a dish shaped foot, then two scales with a zero screw in the scale base and on the far right a Fertig model as shown here. In addition to the scale shown here with its curved brass bands ending in heart-shaped leaves, there exists also an Erhard letter scale base with a sleek square pattern of inlaid brass, see the photo at the bottom right of this page.
Below some more images of this beautiful Erhard & Söhne letter scale.