Block from U+1C80 to U+1C8F. This block was introduced in Unicode version 9.0 (2016). It contains 9 codepoints.
The Wikipedia provides the following information on block Cyrillic Extended-C:
Cyrillic Extended-C is a Unicode block containing Cyrillic characters for facsimile reprinting Old Believer service books. They are (contextual) graphic variants of standard Cyrillic rather than distinct letters.