I believe only the first SP SD7 (ex-demonstrator) had dual controls--I've seen pictures of it with wings painted on both ends like the passenger geeps.

On the Western Pacific, all of the GP7s, GP9s, GP20s, U23Bs, and the first ten GP35s had dual control. I personally never saw it used, however; even on the Tidewater Southern (usually one unit and nowhere to turn it), engineers always seemed to run both ways from the same side. On the other hand, when geeps were used on yard jobs, it was normal to run with the long hood against the cars. In that case, the control stand facing the long hood was used.