ShopLicensePlates has made decoding our real, genuine and authentic old Arizona License Plates easy for you. We have developed an Arizona License Plates County Numbers Key that will help you decipher the two key factors, which are whether the year in question issued a single license plate or a pair of plates;  and it will also assist with determining the appropriate Arizona County Numbers and codes that began in 1922 and ended in 1973. In Arizona, a vehicle registered as a Historic Vehicle which is 25 years old or older may be eligible to use YOM or Year of Manufacture license plates with DMV approval. Because laws vary by State with respect to the use of our real and authentic vintage license plates on an old vehicle, we always recommend that you contact your DMV or visit your local DMV office to confirm that you can use these prior to your purchase.