Would short track ends indicate it's intended for hub gears
Looking at it it looks very similar to my (almost ex) 1930s tandem, which came like you suspect with a Sturmey Archer 3 speed (in my case 3 speed badly modified into a 5 speed) with drum brake.
This is quite local to me: http://www.ebay.co.uk/itm/Steel-Tandem-Frame-/201654936552?hash=item2ef39223e8:g:xigAAOSw-YVXl0DC
Would short track ends indicate it's intended for hub gears?