letter scale

plexiglas letter scale

This letter scale is an invention of Karl Otto Schmidt. The mechanism is described in the German patent DE2321288 of November 7, 1974. The transmission of the vertical movement of the spring scale into a horizontal movement of the indicator, is the main characteristic. The patent was supplemented by the German patent DE2340838 of February 27, 1975. This described a fine tuning of the mechanism with the application of a little magnet. The magnet is applied in this letter scale. The housing and the plate are made of plastic. Besides these 2 German patents,

thin indicator needle

photo from Wedo catalog 1985-1986

this scale was also protected by the American patents US3,799,282 and US3,921,738. In the Netherlands by the patents NL7309984 and NL7316644. In Great Britain by GB1448710 and GB1474417. In France by the patents FR7327373 and FR7401754. Also patents were granted in Japan. A drawing of the patent is presented at the chrome colored oval scale. Before, a yellow version was presented as well. The weighing capacity is 500 grams. The chart is subdivided per 10 grams. In addition to this transparent plexiglas letter scale, also a smoke glass brown version exists. Of both these versions, versions with gold colored mountings at edges and corners were made. Look at the picture above, from the Wedo catalog 1985-1986. Below some more pictures of this letter scale.

zero adjusting screw at back	detail mechanism	bottom
patent numbers at bottom	made in Germany	patent numbers at bottom