The one on the far right is an earlier model flat-feed.
The one in the middle is the latest version, which acts like the Sheaffer "tip-dip" feed. This is your second picture on the right.
The others are plain "comb-feeds" with the comb acting to hold more ink.
There's a fourth version, made near the end of WW2, which has the comb with a solid rounded bottom (I call it "gunboat" because it reminds me of the hull of a WW2 PT boat).
They're all just variations of doing the same thing; getting ink in a smooth "controlled leak" to the point, and changed over the years as improvements came about.
The tops were also stamped differently for style reasons, I guess.