R-115X Edison DD Adapter Arm to play 78s. ORIGINAL. Nice, clean, fully functional arm to lock into the horn in any Edison Diamond Disc phonograph. The front end has the curved slit to accept a Victor Exhibition reproducer or Victrola No.2, or any reproducer that has the standard 11/16″ back hole to lock the reproducer in place. Shown in the photo is an example of this type of adapter.