[JLange]

I recently bought what turned out to be a double of a 1960 Topps #216 Joe Gordon Manager Card. Upon closer inspection of the back, though, there is an additional light brown bar running vertically down a portion of the left side.

Is this a variation or would the extra bar be part of the adjoining card? Does anyone know what the adjoining card would have been on this sheet?
Sometimes it looks to me as if the bar is wholly contained within the border of the card, but that might just be due to slight edge wear.

Any help here would be greatly appreciated!