Mohamed behind the bust in Arabic; Bukhar Hudat ("Lord of Bukhara") in Sogdian script in front of the bust, crowned Sasanian-style bust right / Fire altar with ribbons and attendants; crowned bust left in flames. Imitating Sasanian king Bahram V. 26mm, 2.54 grams. Walker XXVIII-1-2, A 93.
"Mohamed" was a given name of Abbasid Caliph al-Mahdi. Very few coins were issued with this name (instead of the normal "al-Mahdi"), and these coins are very-very rare. These new coins were made with the same dies as the old silver issues, but the silver was replaced with an alloy of six metals: gold, silver, lead, brass, iron and copper. Because of their base look, they were not accepted until their price was fixed by law at 6 Ghidrifi drachms to 1 silver drachm of the same type. Interestingly, the coins became very popular and within a short period of time they were at parity with the silver issues. Within 60 years, the price of the Ghidrifi dirhams rose even more, with 100 silver dirhams buying only 85 Ghidrifi dirhams. This was one of the first (and one of the few successful) attempts to experiment with fiduciary coinage in Asia.