You’ve heard the phrase “a dollar saved is a dollar earned”—but sometimes a dollar saved can be worth hundreds,

even thousands. That’s because collectors pay big money for $1 bills with rare serial numbers.

Each bill has an 8-digit serial number, but not all combinations are common.

Some unusual patterns slip through printing, and those are the ones collectors chase.

Here are a few of the most valuable types:

Ladder – numbers in order (01234567).

Radar – first four digits mirror the last four (22211222).

Super Radar – middle six digits match (23333332).

Repeater – numbers repeat (01570157).

Super Repeater – two digits repeat through (01010101).

Radar Repeater – both a radar and repeater (12211221).

Double Quad – first four digits one number, last four another (00003333).

Seven in a Row – seven digits the same (11111115).

Seven of a Kind – seven digits match, not all in a row (11115111).

Binary – only two digits appear, fewer than seven of either (11313111).

Before spending cash, glance at the serial numbers—you might have a hidden treasure. Curious? Check coolserialnumbers.com for values.