letter scale

This chrome-plated letter scale was made in France by E.S.. I don't know the meaning of this abbreviation. Two characteristic balls are mounted on the base. The dial has a stripe of measure per each gram up to 230 grams. Above 230 grams there is a stripe per each two grams. The weighing range is 250 grams. The pointer is moved by means of a gear wheel and a circular curved toothing. The height of the letter scale is 136 millimeters. The dial diameter is 80 mm. The base measures 95x50 mm. The own weight is 253 grams.
The French postal rate for letters is printed on the dial. 0,50F 0-20g / 0,75F 20-50g / 1 Franc 50-100g / 1,40F 100-200g and 1,80F 200-300g. This rate was valid from April 21, 1930 until 1933. [source: Le Système Métrique pp. 1131-1137].
The dial also has the text: DÉPOSÉ, in other words the design was protected. I have not found a patent or design protection. This letter scale also exists without the postal letter rates on the dial. Instead, there is a ring of many concentric circles. In the middle circle there is also DÉPOSÉ and the abbreviation E.S. That version has a different pattern of stripes of measure: per gram up to 50 grams, per five grams from 50 to 100 grams, and per ten grams from 100 up to 250 grams.
Below some more pictures of this chrome-plated letter scale.