How much are collectible 10 cent horse racing 1974 stamps worth?

Scott # 1528 Most used US postage stamps are worth 20 cents, the minimum amount required to catalog and stock the stamps. Unused will always be worth at least their face value. This stamp can cost you 25 cents mint. Special cancellations and different values are likely to be worth more. Consult a postage stamp catalog, usually available at your local library for exact identification and catalog values.