: In mid-century technical manuals like the Rider-1934 Radio Manual , the string appears within indexed lists or circuit descriptions, likely as a partial reference to specific components or terminal locations.

Depending on the context you are looking for, "Joh.rar" typically refers to:

: In 19th and early 20th-century newspapers and registers (such as the Leipziger Tageblatt and The Gazette and Farmers Journal ), "Joh." and "Rar." were often used as abbreviations for names like Johann or Johannes and specific roles or surnames.