Oldest "Red" (Non-Patinated) Coppers?

While copper is a great metal for circulating coinage (being cheap, durable, and easy to work), it's also a notoriously difficult metal to keep pristine for more than a century or two; it is highly reactive and likes to take on a patina in a way that silver and gold do not. Since getting into ancient coins, I have come to expect and appreciate a good patina, this probably being my favorite:



(Crispus, the oldest son of Constantine the Great, minted c.317)

In this case, the coin was probably cached in a jar or similar sealed container while still a brilliant red; today it is glossy deep black, like a dark chocolate.

That got me thinking, however; since the technology to slab coins in an airtight coffin has only existed for a few decades, there might be a hard limit to how old a copper or bronze coin can be while still being "red". I've seen some pictures of late 18th century coins in full MS Red, but nothing much older. Anybody aware if there is any definitive answer to this question?

Also, in the interest of a fun pile-on, feel free to jump on board with your own oldest "red" coins (raw or slabbed) as well as any gracefully patinated eye candy! Here is my only 19th century coin that is still red; an 1884 rin (1/10 cent) from Japan: