This is a weird effect - found this pack of CR2016's in one of my old stores of batteries. The whole pack is "corroded" though there's no obvious leakage from the cells. Most other cardboard/plastic blister packs of a similar age in the box are fine, but a few others are like this, and they all contain lithium cells.
The cells from at least one pack seemed to test okay at 3V, and the cells are still theoretically "in date".
Anyone know what is going on here?