Quote Originally Posted by Dan Fromm View Post

Practical implications: if the FP has the sandwich, assume that it is original and make sure that the fresnel is between the GG and the lens, also that the ground side of the GG faces the fresnel. If the FP doesn't have the sandwich and you want a fresnel, put it between the GG and the film.
I think you mean between the Ground Glass screen and the eye.

In practice if you add a fresnel to a Crown/Speed Graphic Focus pane that never had one you add it eye side of the GG with the fresnel side against the glass, you need to shim the retaining clips otherwise the focus hood won't fit securely.