#4 does not have any recesses channel (only raised flange (similar to #2)). And #1 has that recessed channel for raised flange of #2.
The suit's material is pressed by raised flange of #4 to the anti friction washer.
That is differed from the scetch above. But the valve on my picture is also little different.
Does the raised flange of #4 fit fairly closely into or around the raised flange of #2?
Doing so would create a spacer for thin trilaminate material and achieve at least one bend of the suit material to anchor and help seal it. (See the SI TECH detailed view in the schematic above.)
Doesn't it makes the most sense to have the anti friction washer next to #1 since #1 is the only part intended to move when tightening?
Anyway, you've got it all right in front of you, so you may be seeing something I can't visualize.
Dave C