CS-Ladders, CS-Looping Ladders, CS-Scattered Ladders, CS-Broken Ladders, and CS-Buildable Ladders.

CS-Ladders.
CS-Ladders are quite popular amongst fancy serial number collectors, as a true CS-Ladder will only occur 16 times in a print run of 99,999,999 Notes. A true ladder is very rare and very sought after. With a good graded Note, these bring a large premium.
CS-Ladders can be a CS-Ascending Ladder or a CS-Descending Ladder. These ladders run sequentially up or down M 01234567 M or M 76543210 M. In a CS-Ascending Ladder or CS-Descending Ladder, the # signifies its starting number. Let us take, for example, CS-Ascending Ladder #0, M 01234567 M. It is a CS-Ascending Ladder that starts from the left at 0 and counts up from there. On a CS-Descending Ladder #9, M 98765432 M, it starts with the number 9 and counts down from there.

CS-Ascending Ladder.
CS-Ascending Ladders are FSNs that count up one number at a time, M 12345678 M. The numbers must be in order. It can start from 0, 1, 2, or 3.

CS-Descending Ladder.
CS-Descending Ladders are FSNs that count down one number at a time, M 87654321 M. The numbers must be in order. It can start from 0, 9, 8, or 7.

CS-Looping Ladder.
A CS-Looping Ladder is eight consecutive digits that start at any position other than position 1 and loop around, M 5678 1234 M. In this CS-Looping Ladder, the first rung of the ladder starts at position 5, counts up to position 8, loops back to postition 1, and counts up to position 4 to complete the ladder. CS-Looping Ladders can count up or count down as long as the sequence is unbroken, M 5432 9876 M, M 3 0987654 M, or M 2345678 1 M.
The way that Currency-Systems numbers CS-Looping Ladders is by the starting number. For CS-Ascending Looping Ladders, the starting numbers could be 0, 1, 2, and 3. For CS-Descending Looping Ladders, the starting numbers could be 0, 9, 8, and 7. You can add the starting position to be more precise such as a CS-Ascending Looping Ladder M 5678 1234 M could be described as CSAscending Looping Ladder #1~5 as the starting number of the ladder is the number 1 and the position it starts in is position 5.

CS-Ascending Looping Ladder.
C CS-Ascending Looping Ladder #0 M 7 0123456 M or M 1234567 0 M. The ladder sequence starts with the number 0, and all numbers are in ascending sequence from left to right starting at any position other than position 1.

CS-Descending Looping Ladder.
CS-Descending Looping Ladder #0 M 3 0987654 M or M 9876543 0 M. The ladder sequence starts with the number 0, and all numbers are in descending sequence from left to right starting at any position other than position 1.

CS-Scattered Ladder.
A CS-Scattered Ladder has all the numbers to make a CS-Ladder, but they are in random order, M 07634152 M.

CS-Broken Ladder.
CS-Broken Ladders are “mini” ladders, or if you imagine a ladder leaning against a building, and the top two rungs and the bottom rung are missing, that would be a CS-Broken Ladder #5 as three rungs are missing but the rest are in place and in order. A CS-Broken Ladder #3 will have 3 numbers in the FSN in sequence M xx123xxx M, a CS-Broken Ladder #6 would have 6 numbers in the FSN in sequence M 123456xx M.
If the mini ladder counts up, it is a CS-Ascending Broken Ladder, M 12345xx M. If it counts down it is a CS-Descending Broken Ladder, M x98765xx M. While only CS-Broken Ladders #6 and #7 may have little if any numismatic value, they are fun to find.

CS-Ascending Broken Ladder.
In a CS-Ascending Broken Ladder, all the numbers are grouped together in ascending order, M x1234xxx M, and can be in any position.

CS-Descending Broken Ladder.
In a CS-Descending Broken Ladder, all the numbers are grouped together in descending order, M x4321xxx M, and can be in any position.

CS-Buildable Ladder.
A CS-Buildable Ladder is a CS-Scattered Ladder with some of the numbers missing. For example, a CS-Buildable Ladder #6 has six numbers in random order in the FSN to start creating a CS-Ladder, M x674325x M, and a CSBuildable Ladder #7 would have seven numbers in random order in the FSN that could create a CS-Ladder, M x1576432 M, and all numbers cannot be sequential at least one number must be out of order. While CS-Buildable Ladder combinations can go on forever and ever, and have little to no collectable value.

Note: This page contains excerpts and basic information from the book "The Green Guide to Fancy Serial Numbers". Please consider adding a copy to your library, thank you.