I posted images of this in the spanish cob forum, but I'm hoping some more people can chime in with some more info and possible date, not that the other interest wasn't appreciated
Appears to be a Mexican 1/2 real minted during the period 1668 to 1697. If an assayer's mark could be noted, a "G" initial would put it in the more restrictive range of 1668 to 1674; otherwise, it's an "L" assayer --from 1677 to 1697. Gaps of years in the production of these cobs exist, even within each assayer's years. These cobs were composed of .931 silver.
Don...