Zands, Karim Khan, 1171 AH, AR Rupi (10-Shahi), Astarabad (Gorgan) mint

[aws22]

Zands, Karim Khan, 1171 AH, AR Rupi (10-Shahi), Astarabad (Gorgan) mint KM#512 (type A)(1163-1193 AH)(1749-1779 AD)
Weight 11 gm
Diameter 23-24 mm
Metal Silver
Obverse is the Farsi couplet: " شد آفتاب و ماه زر و سیم در جهان/ از سکه امام بحق صاحب الزمان ", Shod aftab-O-mah, zar-o-sim dar jahan/ az sekkee-ye Imam be-haqq Sahib-oz-Zamman, meaning: "the Sun & the Moon become gold and silver/ from the rightful Imam the owner of the time". Mint "Astarabad استرآباد " is to the left of the word " zarb ضرب "; part of the date " 117 ۱۱۷ " is at 9 O'clock and the digit " 1 ۱ " is inside letter " N ن " of the word " al-Zaman الزمان " at 8 O'clock.
Reverse: Shiite formula (Kalima) " لا اله الا الله محمد رسول الله علی ولی الله  ", meaning, "no God but God, Muhammad is the messenger of God, 'Ali is the chosen one of God".
Astarabad استرآباد; now called (Gorgan) گرگان‎; it lies approximately 400 km to the north east of Tehran, some 30 km away from the Caspian Sea.
Astarabad is a rare mint for such coin.

Maythem

[THCoins]

I've seen this couplet before, and again value the poetry.
The bright green layer suggests a copper derived corrosion product. Are these coin of a high copper-low silver allow, or would the silver coin have been buried toghether with copper coinage?  What is your impression ?

[aws22]

Thank you Anthony, the silver content of such coin is 0.900 so the green rust could be due to the 10% of copper within the coin or possibly because they are buried together with copper coinage. I tried putting the coin in sour Yogurt for a couple of days as it is slow process that preserves the surface of the coin but unfortunately it did not work. There are many other methods of cleaning but they all lead to losing part of the coin surface. I will seek advice from few jewelers, as I live in Kadhimiya (Baghdad) which is the center of gold & silver jewelry manufacturing workshops.

Maythem

[aws22]

Dear Anthony, I had some help cleaning the coin to the limit that small parts of the reverse are slightly chipped off. All the green corrosion has disappeared.

Maythem