Manuscript

Family name, INITIAL(S). Year. Title. [Material type]. At: Place: holding institution, department (if applicable). Identifier (if applicable).

Example:

Colvil, S. ca.1680. The mock poem, I-II. [Manuscript]. At: Leeds: Leeds University Library, Brotherton Collection. MS Lt 1.

ca. is an abbreviation of "circa", meaning "approximately". You may find that this is used in dates for old manuscripts.