I'd say 'something' is going on, but it could be absolutely anything in my view...even a tool dropped on the die, who knows? There is a tiny fleck sticking out of the right centre of the 8 too, but what can you do, that's all we can say about it? Speaking only for myself, when an overdate or overmark is inconclusive, it should be documented only as an example of a particular die, much as we do for repairs to lettering, etc. until such a time as documentary evidence, or subsequent die examples, prove the case otherwise. The OP coin is not worn to a degree that compromises the details of the underlying shape, suggesting to me that a better example will not reveal anything extra, though I stand to be corrected.
To be true to numismatics we'd be correct to catalogue this kind of coin along the lines of something like 'the 1861 new moon die,' for example, in the same way we have 'dot' pennies!
They will be valid and useful one day in the chronology of the dies, so absolutely 100% worth documenting in locations like these, until such a time as they can be collated together in a future online repository!