Terzemian

Terzemian is a PIE conlang spoken in the area immediately to the west of the Caspian Sea, that is, the Eastern foothills of the Caucasus Mountains.

Proto-Terzemian shares all the features that are common between Indo-Iranian and Balto-Slavic, though Old Terzemian is strictly neither Indo-Iranian or Balto-Slavic.

Terzemian is written in a variety of scripts.

The oldest is known as Terzemian Mnemonic Signs, which is a defective syllabary that distinguishes 12 consonants and 3 vowels. Mnemonic signs use a bi-quinary numeral system, with separate digits for 0 through 4, and a "plus 5" diacritic. This method can be used to count from 0 to 99 on two hands, with the number of fingers extended being 0 to 4, and the extension of the thumb standing for the "plus 5" marker.

After Mnemonic Signs, the Arabic script was adopted and adapted.

During the Soviet era, Cyrillic was required.

A Yanalif reform movement existed briefly, before the modern-day Latin alphabet was designed. For roughly 20 years starting in the late 1980s, there was also "Internet Terzemian", which is a romanization typeable on a standard US keyboard, and representable in 7-bit X3.4 1968 US-ASCII.