In Devanagari, the phoneme [ɖ] is generally represented with ड U+0921
DEVANAGARI LETTER DDA. In historical Devanagari orthography for the
Marwari language of Rajasthan, [ɖ] is represented with a different
letter. In Marwari, ड is instead used for representing [ɽ], an
allographic variant of [ɖ], which is generally written in Hindi as ड़
U+095C DEVANAGARI LETTER DDDHA.
In the Linguistic Survey of India, George Grierson describes the
usage of these characters in Marwari, as shown in the image below:
The character is also shown by Mathias Metzger (Die Sprache der
Vakīl-Briefe aus Rājasthān, Würzburg: Ergon Verlag, 2003):
This Marwari DDA cannot be treated as a glyphic variant of ड and
should be encoded as an independent letter. I have submitted a
proposal, which
contains additional information about the letter and examples of use.
The forms shown by Grierson and Metzger differ slightly. My attempt at
representing the two forms, in adherence with Monotype Devanagari, is
shown below:
I recently learned that this letter was also used in Devanagari orthography
for languages of Sindh. The following specimen shows use of
the letter in Kutchi:
Its usage contrasts with the regular letter DDA:
I would be interested to learn if MARWARI LETTER DDA is used in the
orthographies for other languages.