I think this is pre proper tandem cranksets. If the rear cranks had a spider for the driveside & the nds then it would have the same setup as a modern tandem would. What an awful thing though. (no offence Jack Taylor)
The Rene Herse tandems run the drive chain from the Captain's crank as well. The only think I can think of is front shifting, because they had the lever based front mechs.
