The Miles White half penny is not as common as say, Dragon Slayers or Nova Scotia / New Brunswick issues, and yours is typical of the condition when they are found.
I think if your pictures were as clear as the example you show a lot more could be determined. My bet would be either corrosion (as mentioned by Doug) or perhaps the 8 was impacted (
PMD) at some point.
There is also the chance that it was struck with a partially filled die, but being so worn I doubt it would bring a premium.