It looks to straight and pronounced to be a die crack. IMO. Maybe a damaged die from a previous strike thru or a die gouge.
Well I'm going to keep it because it's definitely some kind of anomaly! So if it was yours and you put it in a flip, how would you identify it? As a strike through, struck with damaged die, or something else?
Until it can be properly identified I would certainly keep it and file it with the unknown category. If you don’t have an unknown category, I’d create one.