These are King Farouk coins minted in silver. Similar patterns are used on gold coins of the period. The denomination is known as 'qirush' in Arabic.
The coin in the picture is a 20 piastres piece dated 1939. See below for more information on denomination and date.
When they are circulated like our picture, the primary value of these coins comes from their silver content. Use Kitco.com to find the current price of silver, then use the data below to compute the value of your coin:
2 piastres, 19 mm diameter, 0.075 troy ounces of silver
5 piastres, 26 mm diameter, 0.188 troy oz silver
10 piastres, 33 mm diameter, 0.375 troy oz silver
20 piastres, 40 mm diameter, 0.750 troy oz silver
If your coin is in fully uncirculated condition, you can add a collector premium over basic silver value, as follows
2 piastres fully unc, add $8
5 piastres fully unc, add $10
10 piastres fully unc, add $20
20 piastres fully unc, add $40
2 piastres dated 1939 are less common and catalog at $12 when well preserved, $85 when fully uncirculated
For instance, suppose you have an uncirculated 10 piastres. The current price of silver is $22.79 US dollars per troy ounce (it changes every day; look it up). That means the basic silver price is 0.375 x 22.79 = $8.50. To get the catalog value for an unc coin, add $20, giving 8.50 + 20 = $28.50. Now, to get actual buy and sell price from this catalog price, apply the concepts on our Terminology page.
You can read the date on these coins using this one-to-one mapping of eastern Arabic numerals. The coin in the photo has two dates: 1939 and 1358. Which one is right? They both are. The 1358 date uses a Muslim calendar based on a lunar (not solar) year and starts when Mohammed was alive in the 600s AD.