Reading and writing aid for distinguishing two interchangeable letters or groups of letters

摘要

Each basic body contains two different symbols each containing the interchangeable letters or groups of letters as a stamp. One of the two symbols has a palpable structure. Both symbols have a congruent outline and represent objects with one symbol on the front and the other on the back or side by side on one side. A separating bar is between the two adjacent symbols. The structure is in the form of an extension protruding from the outline, especially a circular recess in the surface of the basic body.