Recent CRHing Error Questions.

Hey folks,

A couple of weeks ago I posted an error SC quarter. Still unsure about that one, but it got me back into coinroll hunting. I used to do it as a kid to collect the wheats, but now I've started looking for errors as well. In the past 2 weeks I've gone through about $150 - $200 in cents. Unfortunatly no DD's yet! Not even a WAM. (I did get two IH's though, one 1897 with 165 deg. die rotation!) I did find the coins pictured below though and was wondering if the knowledgeble folks here could help me out.

I don't know much about errors, I'm guessing this is a die crack?



Is this just a worn die?




These last two are what I'm really currious about. What caused this? It don't think its post-mint dammage:

1974:







1978:








Thanks for looking and any help would be greatly appreciated!
Ryan