AR double dirham/tanka_Chaghatayid\Ilkhan?

[BACTRIANUMIS]

Heavy and large coin of Tus mint (8.31 g, 31.5 - 32 mm), unearthed in a group with Chaghatayid AR dinars of Buyan Quli Khan and Tughluq Timur. Posted this coin on ZENO as well. Any ideas on attribution will be highly appreciated!

[jkk]

I didn't find it in MWI's Timurids, which is not much comfort. The zuriba is interesting, because it looks like it says minted in SFK (ordering the letters on the logic that a final 'fa' could not be leading into an isolated 'sin').

[aws22]

Dear Bactrianumis, this is my way of looking at your coin, I hope it helps:
Sarbadar, temp. Khwaja 'Ali-yi Mu'ayyad, AH779/1377AD, AR Double dirham, Tus (Tous) mint (AH 763-786 / 1362-1384 AD)
Obverse (First photo): Inside a center circle " Zarb Tus ضرب طوس ", legend around reads: ضرب في شهريور سنه تسع وسبعين وسبعمائه , Struck in the month of shahrivar sanah tisaa wa sabeen wa saba maya (779). The month  شهريور ,  shahrivar, is the 6th month in the Persian calendar.
Reverse (Second photo): inside a hexfoil:  ﻻ ﺍﻟﻪ ﺍﻻ ﺍﻟﻠﻪ ﻣﺤﻤﺪ ﺭﺳﻮﻝ ﺍﻟﻠﻪ , La Ilah Illa Allah Muhammad Rasul Allah, meaning, There is no God but Allah, Muhammad is the messenger of Allah).
Inner margin on four sides, written the names of the four "Rightly Guided" Caliphs, ابو بكر (Abu Bakr), written upside down at top 12.00 O'clock , ﻋﻤﺮ (Umar), at 3:00, علي (Ali), at 9:00, and  ﻋﺜﻤﺎﻥ (Uthman), at the bottom at 6:00 O'clock.
The " Sarbadars سربدار‎ " were a mixture of religious dervishes and secular rulers that came to rule over part of western Khurasan in the midst of the disintegration of the Mongol Ilkhanate (established in AH 737/1337 AD). Centered in their capital of Sabzawar, they continued their reign until " Khwaja 'Ali-yi Mu'ayyad خواجه علي بن المؤيد " (their last ruler) submitted to Timur in AH 782/1381 AD.
Please note, that the city of " Tus  طوس‎ " (Tous), is an ancient city in Razavi Khorasan Province in Iran near Mashhad.

Maythem