Scott 220 And CAPS Over The 2

I'm trying to figure out what is meant about the version of this stamp that have Caps above the number two. Can anyone help explain what this means?

Thanks

If you line up the Scott 220, 220a and 220c (or illustrations of same) and then study the Arabic numeral 2 you will notice that they are not consistent.
On the 220a the left number has a "cap" which is a small flat blob on top of the uppermost curve of the 2. The right 2 has no such protuberance.
On the 220c, both the left and right 2s have this "cap."
On the 220, neither 2 has any top protuberance.

Here is a 220a (not mine) now listed on Hipstamp which shows the left cap clearly. It is kind of a flat top sticking up from the curving arch of the 2. Contrast that with the appearance of the right hand 2. If this were a 220c, then both the left and right 2 would look like the left.

Hope this clarifies.

A good illustration and explanation. One followup question I've always had: Do we know why there is a variety with a left cap, or two caps, but no singular variety with just a right cap?

Here is my triple caps.
6 total, 2 on each stamp.

220c...???

Robert

BrentAbba,
Brookman attributes to progressive failure of the metal of the transfer roll.
So the left side broke first, then the right.

Here's the 220b whose existence has been forever denied...