This article is the result of theoretical and preliminary studies of 240 Shekel (Siglo) coins of the Achaemenid Empire. This valuable collection was obtained by the police of Mazandaran province in 2010 from antique smugglers in Amol city. Currently, these very diverse and valuable coins, which were discovered from a place in the south of Iran and near the port of Assaluyeh, are kept in the Museum in Sari city. Because documenting coins in museums was limited to basic recordings, we had the opportunity to document all the coins in the collection for library studies and comparisons. Documentary of coins was done by measuring, weighing, hand drawing, computer drawing, photography and scanning. After this stage, the main questions and objectives of research were posed. Preliminary studies and comparisons confirmed the attribution of coins to the Achaemenid period. Also, the initial results of the documentation, that's mean examining the details of the image of the coins, including the crown, clothes, weapons, body shape and face details, showed differences in their minting and made it possible to compare them with referable samples. Although in this study, some materials have been proposed to confirm the authenticity and dating and identify the time range of the studied coins, nevertheless, accurate determination of their authenticity and scientific chronology will be possible after more accurate experiments.Coins were invented as a result of the development of societies and the economic needs of human beings. The first coins were minted by the Lydia government. Cyrus the Great, recognized the need to use it, but Darius I minted gold and silver coins for the first time in Iran. The gold coins were called "Darik" and the silver coins were called "Shekel" ) Siglo (. Shekel is a silver coin weighing 5.60 grams. During the Achaemenid period, four types of coinage were minted: 1- Imperial coin 2- Satrap coinage 3- State coins with the image of the emperor 4- Local coins or non-Iranian lands that were under Persian rule. Imperial coinage have no writing; Therefore, their classification needs to be carefully studied and compared with similar samples. The collection studied (Shekel), are under the group of Achaemenid imperial coins. Since the preliminary studies of this collection were very necessary to introduce it to the scientific community, so an attempt was made to make a comparative study of the coins of the Mazandaran Museum with the most important coins found from the Achaemenid period. Coins were studied and documented by referring to reliable sources. In this regard, for comparative studies based on comparison, the characteristics of coins including the appearance of persons on the coin, decorative motifs, Type of clothing and individual symptoms, with similar cases were considered. This almost tedious process eventually led to the creation of a framework for classifying the coins in question. Since the method of documenting these coins in the museum was limited to the initial recordings, due to the importance of the subject, we had the opportunity to conduct detailed studies to address the main questions and objectives of this study. The comparisons made on the coins of this collection confirmed their authenticity and attribution to the Achaemenid period, and the work of documenting showed the difference in their minting.At first, all the study documents, including the history and economic system of the Achaemenid kings, as well as sources about their cultural works, such as reliefs and seals, were collected. The oxide-coated sample was then purged. The oxide layer was then removed from the surface of a number of coins. After this step, the weight of the coins was measured with a digital scale and their diameter and thickness were measured with a caliper. In the next step, the back and front of the coins were photographed with a digital camera and scanner, and then they were technically drawn manually with the help of a computer. If the coin shapes were not obvious due to wear and tear, clear images were created with the help of Photoshop and inverter software for more accurate design. (Figure1). These coins are very simple and the main focus is on the image of the king. The king is armed with a bow, spear or dagger in these coins. With the exception of rare cases, there are depressions on the back of the coins. Sometimes signs and symbols are engraved on the back and on the coins (Figure 8).Achaemenid coins, while simple and similar, have a great variety. Different sources have dealt with their different types and forms as much as possible, but considering that a number of coins in the collection of the Mazandaran Museum in the city of Sari did not have known and completely similar examples, Therefore, they were studied, separated and compared with samples that had the least details in common. From the studies and comparisons made with the samples of other Achaemenid coins, results were obtained that created suitable grounds for identifying and classifying the coins of the Mazandaran Museum. Summary table attached, Comparison of Achaemenid coins of the collection with other coins discovered (Table 1). According to this research, 240 coins belonging to Achaemenid kings have been identified. Recognition of the amount and purity of coins, which is a good criterion for determining the authenticity of coins, was not tested in this study, but the weight of coins, which is usually the standard for mints, was tested. The weight of coins of Mazandaran collection is determined with an average of about 5.60 grams, which is the standard weight of Achaemenid coins. The results of studies have shown that among this collection, there are coins that are similar to known examples. Also, there are coins that do not have similar patterns. This study provided an opportunity to examine the details of the image of coins and compare them with other samples, to classify them and attribute them to one of the kings who owned the coin. shekel coins have a great variety in terms of the image. In other words, the coin of a king has been in different details, which has created different types. The reason for this diversity may have been the existence of multiple mints or the lack of oversight of coin makers. A number of these different species have been identified and introduced in the study collection in Mazandaran Museum One of the reasons for the value of the silver coins studied is that they are a collection. This collection, as a time capsule, introduces a time range with a specific beginning and end. In total, the coins of the seven kings have been identified from the coin-owning kings in this period. In this collection, from Darius I, which basically has three species, one species (Figure 8), from Xerxes, which has two different species, one species (Figure 11), from Artaxerxes I (Figure 14), Darius II (Figure 16) and Young Cyrus, one species (Figure 18), from Artaxerxes II, three species (Figure 22, 23, 24) and in Finally, two types of coins have been identified from Artaxerxes III (Figure 25, 26). According to the information obtained, the period of the study complex was related to the years 522 to 338 BC, which covers about 184 years of the Achaemenid Empire.