Abstract: A reference index is provided for dial type instruments and includes an indicator selectively positioned on the face of the instrument for operation in either of two functional modes. The reference index includes a mounting pivot which is adapted to be secured to the face of the instrument and carries a mounting block that is relatively rotatable about a pivot axis projecting from the face of the instrument dial. Carried by the mounting block is an indicator having an elongated arm which has one end pivoted in the mounting block for relative rotational movement in a plane parallel to the face of the instrument, or perpendicular to the pivot axis. Formed with the outer end of the arm are first and second reference tabs which are adapted to overlie the circular indicia ring of the instrument. The two tabs are perpendicularly disposed to each other and project transversely to the longitudinal axis of the arm.