A dollar bill may not seem like a lot of money, but some are rare and can become part of an investment. The key to knowing if a dollar bill is worth more than its face value is to examine the serial number. Serial numbers are a combination of one letter, eight numbers, and another letter at the end. You can easily find them because they are printed in green and located twice on each invoice. One is near the bottom left of George Washington’s portrait and the other is located to the top right of his portrait. Serial number combinations are key to determining a banknote’s rarity and investment value.

The first letter goes from “A” to “L”. These 12 letters are codes for the cities where they were printed. The last letter indicates the number of times the serial number sequence was used by the Bureau of Engraving and Printing. So “A” means the serial number was run only once. “B” indicates a second time and “C” is the third. The number of letters goes through the alphabet of 26 letters.

Between the letters are eight numbers that represent how many dollar bills were printed in a year. The first printed will be “00000001”. The last one is “32000000”. The lower or higher the numbers, the more they are worth as investments. For example, an invoice with a low number like 00000095or one with a high number 32000022 you can get between $25 and $100.

Also, a specific combination of numbers can add value. If you only have two numbers in the array, such as “2” and “4”, as 22424442. This number is worth a little more than its face value. But, if you have a repeating pattern, like, 24242424gold 24224224, your investment has just increased by approximately $1,000. This special combo is called a “binary ticket”.

You can also get a set with three numbers, like “2”, “4” and “7”, you can have them in no special order, like:27244727, gold 59577975 Of course, if they follow a repetitive order, they are worth more. You should know that a combination of two numbers will be more valuable than the combination of three numbers. These are called “trinary bills,” which could only cost $3 or $5.

Another type is called a “ladder”, which is a direct count from 1 to 8: 12345678 or vice versa: 87654321.

A “radar” ticket reads the same numbers back and forth, like a mirror: 14622641. A “super radar” ticket only includes two numbers, with the same only at the beginning and end: 59999995. Radars can be around $25 while super radars can be around $70.

Two or more separate bills with consecutive serial numbers, such as 25348793 and 25348794They are two bills printed one after the other.

“Doubles” occur when you have two of the same numbers: 33774499. A “double quad” is two sets of four of the same number: 33335555. Even a ticket with a number repeated eight times: 44444444 could bring $500.

You can also find a “star note”. If you see a star at the end of a serial number, it means it’s a replacement invoice for one with the same serial number that was damaged.

Special combinations of dollar bill serial numbers range in value from a few dollars to a few thousand. My advice is to go to your bank and ask for a dollar “strap”, which is a pack of 100 dollar bills. Check them out and see what serial number patterns you can find. Sometimes a fresh new pack of dollar bills will arrive at a bank directly from the Bureau of Engraving and Printing. So you might have a good chance of finding back-to-back bills, which could net you a few more bucks if you sell them to a collector. Just remember that any invoice with a special serial number is a rare item. Now, you have a good reason to check the dollar bills in your pocket or purse.