Although A. Ishraq-Khavari (Ganj-i Shayegan 42-45) and A. Taherzadeh (Revelation of Baha'u'llah 1:244-245) date this Tablet to the Baghdad period, I think internal evidence clearly points to its having been written *after* Baha'u'llah had left the city of Baghdad. In fact, the autumnal imagery (gusts of wind denude branches of their leaves) suggests the possibility that it is being written back to Baghdad or Iran from Istanbul in fall, 1863.
For instance, Baha'u'llah says dar i:n vaqt kih t.ayr-i baqa' az ard.-i `Iraq parva:z namu:d -- "in this time, when the bird of eternity has flown from the land of Iraq . . ." This sounds to me as though he has already left. It is true that he also says of himself, 'that breeze shall not again blow in this land (dar i:n ard.),' as though he is still there. But in this case the 'land' referred to could be simply the sublunar realm, and the point could simply be that Baha'u'llah would never again be accessible to people in the way he had been in Baghdad, where he hung out in cafes and where Babi pilgrims could easily come down from Kermanshah for a visit.
If I am correct, this tablet then belongs with the Tablet of the Bell, which Denis MacEoin has has translated, and the Mathnavi or rhymed couplets, in the category of works written in the Ottoman capital in fall, 1863. Certainly, I would date it after May 3, 1863. It could have, like the Lawh-i Hawdaj, been written on the way to Istanbul. But the autumnal imagery does seem to me suggestive for dating purposes.
Baha'u'llah had already made his April-May 1863 Ridvan declaration that he was the Return of the Bab, and he in this Tablet fairly openly claims that his advent was predicted in past scriptures. He is the one from Persia (I read "`Ira:q" here as `Iraq-i `ajam and so translate it as Persia) who speaks in the melodies of the Hijaz--i.e. an Iranian who writes in Arabic. I am unaware that anyone has yet identified the precise prophecy to which Baha'u'llah refers here, though this phrase is fairly common in his writings of the Baghdad and early Edirne periods, and has been discussed at length by Steven Lambden.
The tablet is full of emotion and the grief of parting, and good effect is gained from the switch away from the formalistic Arabic prose poetry at the beginning the more intimate, chaste Persian prose thereafter (which recalls in some ways the Persian Hidden Words, though this work is more open about Baha'u'llah's messianic aura).