The demise of Imam Razi Abdullah in Salamiya in the year 876AD marks the end of the concealment period known in Ismaili historiography as the dawr al-satr.

Imam Razi Abdullah was born on the 12th of Shaban, 210AH (825AD), in Mahmoudabad (formerly, Muhammedabad), near Rey (now Tehran).

Imam Taqi Muhammed was born on the 12th of Rajab, 174AH (790AD), in Muhammedabad.