1939 Egypt 5 Piastres Silver Need Some Help

The 1939 Egypt 5 piastres I have has a security edge, which looks like an ordinary reeded edge but with a groove right around the centre of the edge, with little dots regularly spaced inside the groove. To someone who's never seen a security edge before, it can look like "two coins stuck together".

Here's the pic of mine, showing the edge:


Security edges were used in countries where it was feared that forgers and clippers (people who trim away the edges of a silver coin, then put the coin back in circulation, and keep the trimmings to sell as scrap silver) might be able to make a passable imitation of an ordinary reeded edge. The elaborate grooved pattern gave extra "security", hence the name.

Such edges are still used on the coinages of some countries, notably Hong Kong, even though the coins are no longer made of precious metal so clipping is no longer a problem.