This coin shows characteristics of a post-Mauryan/post-imperial coin. The very low weight does not appear in Series IVa coins (corresponding to Shaishunaga dynasty) but is typical of Series VIII post-Maurya coins (Gupta & Hardaker, p. 187). The reverse mark is unlikely to be a six-armed variant (no other examples are documented) but may be a partial mark 473 (taxila symbol). The bull (mark 58) in inconclusive as this appears in most karshapana series. Mark 374 (crescent above three arched hills) appears only in Series VIa, VIb and VIII (Gupta & Hardaker, p. 265). The coin does not resemble any VIa or VIb types in the catalog (op. cit.) but given the low weight and appearance of base silver composition, this is almost certainly a Series VIII (post-Mauryan) type.
Work cited:
Gupta, P. & Hardaker, T. (2014). Punchmarked coinage of the Indian subcontinent: Magadha-Mauryan series. IIRNS Publications.