The cluster of arrows & bow in this style is pretty much unique to the Spanish issues. I would take issue with calling it a "cob", though. The flans for these were not chiseled off the end of a cast silver bar of convenient-diameter. I don't know if any of these AR denominations were among the early milled experiments - Spain was experimenting with 'ingenios" very early-on, compared to other contemporary world powers. This may surprise those who are mainly familiar with the crude dump-style vellon maravedis which were so often C/M'ed for revaluation during the 17th century - the "resellos". It will occasionally surprise someone when they find one or more of these revaluation C/M's on a neat, obviously milled Æ coin which otherwise appears as though it's of more modern originthan the date on the C/M.
Cobs were minted in mainland Spain, too. Evidently, a combination of crude instrumentation and a need to quantify enormous amounts of silver imported from Potosi and other New World sources faster than it could be coined there led the mints to literally cut corners, at least occasionally. But you're right that this is not a cob - it's most likely struck on a relatively regular (for the era) round flan created by either punching rounds out of a sheet of metal hammered to the appropriate thickness or cast nearly sphere-shaped and subsequently were hammered flat before minting. This accounts for the irregularity you see in the rim - this piece appears also to have been bent and "straightened", probably repeatedly.
With Spanish issues I've never heard of any coin referred to as a cob except those minted in the colonial mints. And the vast majority of the silver and gold that was exported to Spain from the new world, was already in the form of cob coins before it was ever shipped. Once it got there, the coins (the cobs) were melted and minted again.
