As BMC 574 (most probably).
Edge reads 'NVMMORVM [ ] FAMVLVS [ ] 1691 [ ]', where [ ] means not discernible, although there does not appear to be the space for two star stops and so probably BMC 574.
This example is not dated in the exergue but is dated 1691 on the edge. The 1691 issues listed in Peck all include the date in exergue whereas the 1690 issues are known to be dated on the edge only, with the exergue empty. Therefore, this coin appears to be a 'mule' type with 1691 on edge only. If so, unrecorded and presumably very rare.
Nearly Very Fine for issue and totally free of the usual surface corrosion. Copper plug still intact.