It's probably the same sign as that of IPA for postalveolar voiced
fricative (or Old English <g>), defamatorily implemented to designate
phonemic [dz] cluster in Slavic studies (the same sign with a "reversed
`" above renders [d'z'] -- i. e. palatalized or alveolo-palatal [dz]).
> (Just a bit of info: an inverted circumflex is called a
> "hacek". And isn't the "cedille-like" extension on the "z"
> actually a cedille?)
>
Sergei