It's a Simplex (probably) or Cyclo bandspring POS, which was made obsolete by the Campagnolo Gran Sport, the first modern parallelogram rear derailleur. Note the normal-low reverse shift, meaning that if your cable slipped or snapped, the derailleur cage and chain would go right into the spokes, which could ruin your whole day on a fast descent during an attempted 4-5 shift.

The original 1960 Varsinentals came with the obsolete Simplex suicide shifter up front and the equally suicidal Simplex bandspring in back, because Frank Schwinn told Keith Kingbay to save $1.27 by using those junky components instead of the vastly superior Huret Allvit rear and matching front. In 1961, Kingbay got the Huret brothers drunk on martinis at a steak house in Chicago, and they agreed to match Lucien Juy's price.