Caldwell Non-Tilting Window Balance

I need help identifying the correct replacement window balance for two different non-tilting window balances. They are both Caldwell brand. They are identical in length and width: 24" long (excluding the plastic ends) by 9/16" wide. One is marked "23 3 LO Caldwell", the other is marked "24 4 LO Caldwell" and has a heavier and longer spring. There are no other markings that I can find.

Thank you!
Spencer