Variant A indicates that the letters of U.S.S. are widely spaced, or there is unusually wide spacing between wording (“wide” is defined as sufficient space for another letter plus at least a little more). The difference between an A variant, a B variant, and normal spacing can be very subtle visually. Sometimes you will have to get out the millimeter ruler.
The following cancel is classified as Type 3 (AC-TBT)
Variant B indicates that the letters of U.S.S. are narrowly spaced, or there is unusually narrow spacing between wording (“narrow” is defined as insufficient space for another letter).
The following cancel is classified as Type 3s (B)