The following cancel is classified as Type 3as

In the above example, no killer bars are present. In order to kill the stamp, a
target killer (concentric circles) was used.
The following cancel is classified as Type 3b (BC-XTX)

In the above example, the top and bottom killer bars are missing (that's what
the "X" in the "XTX" means).
The following cancel is classified as Type 5bhks (XOX)

In the above example, the top and bottom killer bars are missing.