How to Identify the Dirham of Hasan ibn Zayd

Start by confirming the basic form. This is a purely epigraphic Islamic dirham: both faces are covered in Arabic script with a central legend enclosed by one or more concentric circular marginal legends, and there is no portrait, animal, or figural device anywhere on the coin. If you see a ruler's bust or a fire-altar, you are looking at a different, earlier Sasanian-style issue, not this reform-type dirham.

Sort out the two faces. The religious side (the obverse here) carries devotional text — characteristically the profession of faith, that there is no god but God alone, together with Qur'anic phrasing in the margin. The authority side (the reverse here) is the one that identifies the coin: it names the issuing power, and on this type it is the appearance of Hasan ibn Zayd and Alid titulature, rather than a plain Abbasid caliphal formula, that pins the attribution. Reading, or having someone read, the authority legend is the single most important step.

Check the physical coin against the dirham standard. Expect a broad, thin silver flan, roughly on the order of 25–30 mm in diameter and only a couple of grams in weight, often lightly toned and frequently struck a little off-center so that part of the outer circle runs off the edge. That soft grey silver look and wide flan are normal; a thick, heavy, or yellowish piece is a warning sign that the coin is not what it claims to be.

Locate the mint and date within the margins. On these issues the mint name and year are written out in Arabic words, not as numerals, and they sit in the circular marginal legend rather than the center. Tabaristan-region mints and the Alid ruler's name are the diagnostic combination; an otherwise similar coin naming only the Abbasid caliph, or a different Caspian ruler, is a look-alike from the same tradition rather than this exact type. Because the whole attribution hinges on script, compare the legends carefully against a specialist catalog of Islamic or Tabaristan coinage.

Apply sensible authentication cautions. Genuine coins are hand-struck, so expect slightly irregular flans, uneven relief, and crisp but not machine-perfect lettering; be wary of cast copies with soft, blurry script, seams, or air bubbles, and of tooled pieces where letters have been re-cut to "improve" a weak legend. Weigh and measure the coin, examine the silver surface for casting texture, and for any significant purchase seek an expert reading of the Arabic and, where appropriate, a professional opinion, since so much value and meaning rest on the exact wording.