1974 Kennedy half dollar no mint mark with possible error?

Can anyone help me out with this? There is no mint mark and I found this on reverse. wel

 

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Looks like a contact mark from another half dollar. Edge is reeded so that's why the mark looks like a gear. Philadelphia has no mint marks.

 

I thought so too but it's too big to be the imprint of another coin.

 

Definitely reeding mark from another half. It can be a rolling hit and the mark looks bigger or squiggly.

 

I think it looks pretty cool but am of the same opinion already stated in that it's contact marks from another coin. Can you tell if those marks are raised from the field by chance?