I am speaking of the Nikkor T ED lenses in Copal 3 shutters for 8x10 cameras. The 600mm/800mm Nikkor is probably an older design than the 600mm/800mm/1200mm Nikkor. The latter has extra markings for 1200mm---on the shutter and on the rim of the front element. My question is this: Is the glass in the front unit of the 600/800mm of exactly the same design and materials as the front unit of the 600/800/1200mm?
Put a another way, should either front unit work equally well with any of the rear units?