What Is It? Ottoman Empire (Id: Imitation Ottoman Jewelry Replica)

Those three differences, to me, all point to the same conclusion: that this is not a genuine coin, but a jewellery replica.

Genuine coins of this type, and other 19th century Ottoman coins, have been prized as jewellery-pieces since they were made in the mid-1800s - which is why it's really hard to find a genuine example of this coin that doesn't already have a hole punched in it. This strong demand means people will settle for replicas.

Some of these "jewellery replicas" are quite crude and obvious copies, and not even made from real gold. Just do a forum search for "imitation Ottoman" and you will find plenty of threads with them. Others are made from real gold and much more closely align with the original designs. This is one of those latter types. The "strange mark" will be the stamp or symbol of the person or company that manufactured it. In Dubai, for example, it is perfectly legal to make counterfeit/replica gold coins and sell them in the gold market, so long as the fakes are actually made of gold and clearly stamped with their correct fineness; I suspect that the "dint" near the hole is actually a fineness-stamp. These replica-coin-makers make their profits by producing replica coins that are either slightly less finer gold than genuine coins (eg. a 21k sovereign instead of 22k) or, as in this case, make the replica coin slightly underweight.

Since they're not genuine coins, jewellery replicas don't have any collector premium above bullion value.

I can't see any letters or numbers on the dint.