Brokage Or Broadstruck? (1999 Cent)

to CCF. I agree with an off-center strike.
John1

Not to step on anyones toes, but Zinc rot isn't a disease. it's a reaction between the copper (anode) and the zinc (cathode) and water/moisture/humidity as the electrolyte causing a galvanic cell and rapid corrosion of the zinc.

if you knock off the blueish stuff with a soft paint brush, (the bluish crusty stuff is Hydrozincite, crystaline zinc caused by water basically). then keep it dry from here on and protected, the exposed zinc core will dust over with a light layer of white zinc oxide, and it will stop. if that gets knocked off, it will create more zinc oxide to cover the exposed zinc and protect it from loss again. you can leave the Hydrozincite it won't grow unless there is moisture, but it's kind of unsightly.

Zinkpest ("Zinc Pest" or "zinc rot") is an old term for a destructive, intercrystalline corrosion process of zinc containing lead impurities. Moisture is the lead contributor to the breakdown.
Weissrost ("white rust") is an old term for Zinc corrosion, old war medals, and die cast models are affected by this, if you don't wash them at all and then handle sparingly, and try to keep humidity of the storage environment below 65%, it can be slowed to a crawl or even stopped.

It's the moisture and handling in circulation that is the rapid death sentence to exposed zinc of split plating, not the split plating itself. no electrolyte = no galvanic cell reaction no zinc rot, and minimal zinc dust even.
if it's constantly handled and getting wet from humidity, skin moisture, or water, it deteriorates rapidly under the copper and falls apart.

Main point is it can be maintained and controlled. Here's a 1990 with severe split plating, been in my custody for 32 years now, and following the rules. It's not a death sentence. this coin will still look like this in another 32 years and longer with no change.