letter scale, designed by Gabriel Riddle
Gabriel Riddle designed this letter scale and received a design registration on the design. It is Registered Design No.113, which was granted on November 28, 1839. The term of this protection was three years. The letter scale is described in Mechanics' Magazine, No. 853 of Saturday, December 14, 1839 on page 178 and a drawing of the letter scale is featured on the cover of the magazine. In Germany attention was paid to the letter scale of G. Riddle as well, in Dingler's Polytechnischen Journal 1840, Band 75, Nr. LXXIII, (pages 430-431) en Figure 15 at Tab.VII. The letter scale in the design goes up to four ounces, which is more than the two ounces version shown here. Strangely enough, the text of Mechanics' Magazine states that the scale goes up to three ounces. According to the article, in 1839 1 in 1,000 letters was heavier than ½ ounce, and 1 in 50,000 was over 1 ounce. The weighing range would therefore be more than sufficient. The scale of this letter scale is subdivided by ¼ ounce. This value was used for letters abroad.
In the design drawing, the lower part of the round upright has been made flat. With the later actually made scales, this is no longer necessary due to a design adjustment, and the upright is kept nicely round. On the back of the counterweight is a protrusion that serves as a stop of movement in the unloaded situation. Without this stop, the letter scale swings out for a long time, partly due to the beautiful knife edge bearing and because the letter holder acts as a second pendulum. Copies of four ounces are slightly better known, they are 190 millimeters high and have a base diameter of 73 millimeters. There are different versions. Scales with mostly smooth surfaces like the one shown here, and gilded ones with floral decorations engraved in them. Also shiny brass versions with the English letter post rates above the weights on a somewhat higher made scale of measurement.
back of the letter scale
