Technically, the inscriptions on Ottoman coins are Turkish. Most of the letters and many of the words are borrowings from Arabic. A few letters are added to the standard Arabic alphabet to stand for sounds found in Turkish but not in Arabic. In the post-Ottoman period, modern Turkey has adopted a Roman-style alphabet.
For westerners like us, struggling to read the coins, there is little distinction to be made between Arabic and Ottoman Turkish. Still, it is a real distinction and obvious enough to native speakers. A similar situation exists with Persian inscriptions as found on Iranian and Indian coins.
Hair-splitting seems to be the order of the day here on Numista, so I thought I'd take the opportunity to split this one.