Aleikum Salam Ibrahiim
it's not a "prayer cup" called in Arabic "tasset el kha'da" or "tasset el rhaba",
either "Islamic talismanic bowl" or "medicine bowl"
it's my specialty, I have a not too bad knowledge about those particular items
the main thing to identify it
- must have engraving inside the bowl, and may be outside
- engraving must contain Surat (or part) "Ayat al-Kursî"
- the oldest and rear one, have the Salomon seal, on the middle
after, there is a long speech possible about it, but it will bother everybody,
it's a field of few more or less .... crazy for
best regards
à +
Dom