PS, there is a manuscript copy of the Māṭharavṛtti (Sāṅkhyasaptatyā vṛtti) in the Wellcome Library, London.  Shelved at

• Wellcome MS Indic α 915 (= alpha 915)

and described at serial no. 462, p. 114, of v.1 of the Handlist of the collection (also in The Archive).

Best,

Dominik Wujastyk