But on the 1940 film, 'The Long Voyage Home', Toland used a different technique to achieve a similar effect using a split diopter to achieve this shot.
At their core, split diopters enable dynamic compositions along the Z axis of a frame rather than point an audience's attention to one subject, a split diopter creates multiple planes of action.
This is because the diopter portion of the image will have a very shallow depth of field, and a higher stop will make it a little deeper so that focus issues can be more easily avoided.