Almost 30 years ago when he was in the sixth grade, Mohamed Natw found a banknote in his house—but it was not like the ones in circulation at the time. He decided to take it with him to school to try to use it to buy something from the school’s canteen. And even though he was not surprised when the staff did not accept the note, he began to look for other ways to use it.

Since then, Natw—now an expert in currencies and owner of the Islamic Dinar Museum in Mecca—has been thinking a great deal about old money. Delving deeper into the world of currencies from the past, he managed to find as many as he could, until he had eventually amassed a collection of 5,000 coins. He then decided to preserve them in his own museum which, in addition to old Islamic coinage from silver dirhams to gold dinars, also houses a collection of antiquities, old weapons, shields and crafts.

The museum is now home to 3,400 silver dirhams and 760 gold dinars from the Arabian peninsula covering a period from the dawn of Islam to the Saudi era. Natw told Asharq Al-Awsat that among the collection is a golden dirham from the Abbasid period counterfeited by the crusaders—one so rare that it is worth millions of present-day Saudi riyals.

Europeans wanted to counterfeit Islamic coins that were minted during the Abbasid period to undermine the Caliphate. But their lack of knowledge of Arabic writing led to mistakes being made with some of the letters.

However, given that most people at the time were unable to read and write, the coins passed through people’s hands, who took them as dinars minted in Islamic lands—though in reality they had a European origin.

Speaking of the art of authenticating old coins to prevent forgery, Natw says that practice, experience and specialist equipment are some of the most important tools at a coin expert’s disposal. He said old coins were especially vulnerable to alteration or forgery and that lack of experience among some can lead them to buy the coins from a fraudster—whether they know the coin is fake or were themselves tricked.

Experience allows for a coin to be authenticated simply by holding it and feeling the prominence of the writing on it, Natw said. It can then be verified using specialist equipment such as a magnifying glass to view the grains on the surface.

Coins in the days of the Abassid Caliphate began with the copper fils, followed by the silver dirham (worth 20 fils), and then the golden dinar (worth 20 dirhams). Natw points out that whether in days gone by or today, the gold dinar has always been worth more than the dirham.

Saeed Al-Ghamidi, owner of “The Small Museum,” as he calls it, which he moves from city to city in Saudi Arabia, told Asharq Al-Awsat that over the last 32 years he has collected coins and banknotes going back to pre-Islamic times, most of them Byzantine and Roman in origin and some even predating the birth of Christ by 150 years.

Ghamidi has travelled the world in search of old and rare coins, a hobby that began after he got hold of some rare American coins while he was stationed in the US with the Saudi Navy. Ghamidi admits the hobby has become a part of him, one he will not be able to stop until the day he dies.

He also talked about his collection of old banknotes, called barat, which were first printed during the Ottoman period. He said that when King Abdulaziz, the founder of the Saud dynasty and the first king of modern-day Saudi Arabia, entered the western Hijaz region of the Arabian peninsula—which includes the holy Islamic cities of Mecca and Medina—he inscribed the Hijaz seal on some of the newly-printed Saudi Arabian notes, including the 20 and 40 barat. However, these days, Ghamidi said, a 5 barat note with the Hijaz seal printed on it is considered rare, and can fetch some 1,000 riyals.

He also noted that old Saudi coins have been through many phases. The Arab riyal was minted during the reign of King Abdulaziz in 1927 and had the phrase “King of the Hijaz and Najd” stamped on it. Hajj bonds were first issued during his reign as well. As for the rarest coins, Ghamidi said that it is the ones with mistakes on them—typographical errors, for example—that are actually the rarest and most valuable, noting that a US dollar bill with a mistake printed on it was sold by a British auctioneer for 80,000 dollars.