Block from U+1DC0 to U+1DFF. This block was introduced in Unicode version 4.1 (2005). It contains 58 codepoints.
The Wikipedia provides the following information on block Combining Diacritical Marks Supplement:
Combining Diacritical Marks Supplement is a Unicode block containing combining characters for the Uralic Phonetic Alphabet and Medievalist notations. It is an extension of the diacritic characters found in the Combining Diacritical Marks block.