Am I seeing double...no, it is just a Double Stop

Double Stop: Double stop is the playing of two pitches at the same time to create the effect that the two notes are being played at the same time. This stopping, a.k.a. fingering, of the notes allows the two notes to sound simultaneously despite the fact that the curve of the instrument forces the performer to play the notes in succession. To correctly create this effect, the performer must play the lowest string first before moving the bow to the other strings. Also, this can be performed with more than two notes, then called multiple stops. This double stopping technique was described in Ganassi’s Regola rubetina (The New Harvard Dictionary of Music, 253), written in 1532 as the first important tutor for the viola da gamba according to Patricie Connelly.
Sixteenth and seventeenth century composers Marini and Biber use double stops extensively in their works, however the most celebrated works with double stops are the violin and cello works by Bach written in the 18th century. In 19th century music, the technique is also used frequently by Paganini.