On the 50c coin, it looks to me like a piece of foreign material got between the planchet surface & the die prior to being struck, then the foreign material fell away leaving the defect you see now, usually referred to as a strike through.
If you can tell by close observation that the defect is lower than the surface of the rest of the coin, then I'd be 99% certain that it's a strike through foreign object.
More very interesting reading here, scroll down for some strike through examples:
https://www.thepurplepenny.com/page...type=productGood find by the way!
It's definitely an error worth hanging onto.

life is a mystery to be lived not a problem to be solved
Edited by Nevol
06/28/2019 7:18 pm