Your state quarter could be worth a lot more than just 25 cents.

The U.S. Mint State Quarters were created from 1999 to 2008, with coins for five states released each year. Those coins have one of three markings — “D,” “P” or “S” — which signifies where they were minted.

D stands for Denver Mint, P stands for Philadelphia Mint and an S is for those created at the San Francisco Mint. Coins marked with an S and coins marked with an S that are silver-proof are more likely to fetch more than D or P coins.

Silver-proof coins, which are made of 90% silver, change in value depending on the current price of silver, according to Nationwide Coin & Bullion Reserve.

State quarters in mint condition marked with a D or a P are worth only $1 in 10 states, and are worth an average of $1.71 each, according to Coin Trackers. You’ll get the most, around $3.50, for Connecticut, Delaware, Georgia, New Jersey and Pennsylvania state quarters.

On average, you’ll receive $7.03 for an S mint quarter. The lowest-value S quarters are worth $4, but you’ll likely get the most for Ohio, at $15.

S coins that are silver proof are worth the most, at an average of $14.57 a quarter, according to data from Coin Trackers. But while you’ll only get $8.50 for a Delaware coin, your Pennsylvania quarter could fetch $55. You can get $50 for a Connecticut or New Jersey quarter. If you have a full set of silver-proof coins, the collection could be worth $1,500, according to Metro Metal Detectors.

California’s state quarter ranges from $1.10 to $11.

How can you tell if your state quarters are silver-proof? There are a few subtle factors that may give it away, according to coin-collecting experts.

“These coins can be differentiated by the silver edge of the coin, the slightly greater weight of 6.25 grams, or by the official US Mint packaging,” according to My Coins Guide, noting that the latter may have indicated the quarters’ makeup when shipped as part of a set.

There are multiple other factors that can increase a state quarter’s value, including for those that are in circulation.

For example, some 1999 Delaware state quarters have a defect from a die break. On those quarters, there is a line from the horse’s mouth to the left. While these used to be worth up to $500, the price has now dropped to about $10 to $20 a quarter after it was discovered how common the error was.

But no matter the current price, it’s wise to hold onto your coins. You never know what it might be worth one day.