After Emam Reza (A.S.) was laid to rest a wooden Sandouq (case) was placed over his holy grave. In the 6th century A.H, during the rule of Sultan Sanjar, a Sandouq made of silver replaced the old one. The famous north African traveller Ibn Batuta, who passed through the holy city of Mashhad in 734 A.H./1333 A.D, has written in his travel account about a wooden case plated with silver and covering the blessed grave. With the coming to power of the Safavids the second king of the dynasty, Shah Tahmasb I, coated the Sandouq with gold and during the reign of Shah Abbas I, it received another gold coating and inscriptions by the famous calligraphist Ali Reza Abbasi.
In 1143 A.H., Nader Shah Afshar applied another coat of gold which, however was later removed by his grandsons Nader Mirza and Nusratullah Mirza, who melted it to make the "Naderi Coins".
In 1932 A.D. The wooden Sandouq was removed and transferred to the museum and in its place a new Sanduoq, made of 11 slabs of exquisite marble, was installed over the grave. The marble, which is from the Shandiz quarry near Mashhad, is green in colour with a yellowish hue. This Sandouq is 210 centimeters in length, 160 centimeters in width and 95 centimeters in height. The same marble was also used for the floor inside the Sandouq.
source : http://www.imamreza.net
