characterized by historical or archaizing spellings. Most notably, it continued to reflect the pronunciation that preceded the widespread Iranian lenition processes, whereby postvocalic voiceless stops and affricates had become voiced, and voiced stops had become semivowels. Similarly, certain words continued to be spelt with postvocalic and even after the consonants had been debuccalized to in the living language. The Pahlavi script consisted of two widely used forms: Inscriptional Pahlavi and Book Pahlavi. A third form, Psalter Pahlavi, is not widely attested. Inscriptional Parthian Although the Parthian Arsacids generally wrote in Greek, some of the coins and seals of the Arsacid period (mid-3rd-century BC to early 3rd-century AD) also include inscriptions in the Parthian language. The script of these inscriptions is called inscriptional Parthian. Numerous clay fragments from Arsacid-era Parthia proper, in particular a large collection of fragments from Nisa that date to the reign of Mithridates I (r. 171–138 BC), are likewise inscribed in inscriptional Parthian. The bilingual and trilingual inscriptions of the early (3rd-century AD) Sassanids include Parthian texts, which were then also rendered in inscriptional Parthian. The Parthian language was a Middle Iranian language of Parthia proper, a region in the north-western segment of the Iranian plateau where the Arsacids had their power base. Inscriptional Parthian script had 22 letters for sounds and 8 letters for numerals. The letters were not joined. Inscriptional Parthian has its own Unicode block. Inscriptional Pahlavi Inscriptional Pahlavi is the name given to a variant of the Pahlavi script as used to render the 3rd6th-century Middle Persian language inscriptions of the Sassanid kings and other notables. Genuine Middle Persian as it appears in these inscriptions was the Middle Iranian language of Persia proper, the region in the south-western corner of the Iranian plateau where the Sassanids had their power base. Inscriptional Pahlavi script had 19 characters which were not joined. Psalter Pahlavi Psalter Pahlavi derives its name from the so-called "Pahlavi Psalter", a 6th- or 7th-century translation of a Syriac book of psalms. This text, which was found at Bulayiq near Turpan in northwest China, is the earliest evidence of literary composition in Pahlavi, dating to the 6th or 7th century AD. The extant manuscript dates no earlier than the mid-6th century since the translation reflects liturgical additions to the Syriac original by Mar Aba I, who was Patriarch of the Church of the East c. 540–552. Its use is peculiar to Christians