A banknote with a serial number which each next digits move up or down. There are two type:

1. Circular: The digits at both ends of the serie also move up or down each other, for example "76789876"
2. Non-circular: The digits at both ends of the serie does not move up or down each other, for example "54345678"

A perfect ladder would be all next digits up or down, such as "12345678" or "76543210".

A banknote that has a serial number near to the beginning of the serie (view High serial number for the reverse case). It's necessary to know the serial interval (or its estimated), because the serie can start in any number, nonetheless generally starts at 1.
These pieces often has a higher numismatic value to others at the same condition, based to the difficulty, and the value is higher as the serie is near to the start.

Currently there are no defined conditions yet to check whether a serie is low or not. However, this website provides the guideline based on Relative amount of low and high serial number, which there are four amount of pieces that define four intervals.
General Interval
The general low serial interval are pieces within all levels, from the beginning of the 4th Level and ending of the 1st Level.


This piece, identified as bbcv10bs-da07-r7 has a serial interval R6000001-R9000000 with 3,000,000 pieces (excluding damaged and not used). The interval for low serial number is R6000001-R6001808 with 1808 pieces. Photograph credits: Mercadolibre: unreal86

A.- First Interval (1st Level)
The interval is based on the first level of the conditions. This level can be considered the more feasible.


This piece, identified as bbcv100bsf-aa02-a8 has a serial interval A44400001-A90000000 (estimated) with 45,600,000 (estimated) pieces (excluding damaged and not used). The interval for low serial number level 1 is A44402941-A44407104 with 4164 pieces. Photograph credits: José Manuel Piñeiro ✝
B.- Second Interval (2nd Level)
The interval is based on the second level of the conditions (4.000 pieces for 90.000.000 issues).


This piece, identified as bbcv20bs-fd01-t7 has a serial interval T9000001-T9999999 with 999,999 pieces (excluding damaged and not used). The interval for low serial number level 2 is T9000184-T9000521 with 338 pieces. Photograph credits: Sergio Sucre Castillo: Billetes del BCV
C.- Third Interval (3rd Level)
The interval is based on the third level of the conditions (1.000 pieces for 90.000.000 issues).


This piece, identified as bbcv10bs-fa01-a7 has a serial interval A0000001-A9999999 with 9,999,999 pieces (excluding damaged and not used). The interval for low serial number level 3 is A0000059-A0000437 with 379 pieces. Photograph credits: Mercadolibre: business_paraguana

D.- Fourth Interval (4th Level)
The interval is based on the fourth level of the conditions (100 pieces for 90.000.000 issues). This can be considered as the harder or least feasible.


This piece, identified as bbcv100bsf-aa07-bn8 has a serial interval BN00000001-BN90000000 (estimated) with 90,000,000 (estimated) pieces (excluding damaged and not used). The interval for low serial number level 4 is BN00000001-BN00000100 with 100 pieces.