There was a (bad) movie called “Time Rider” where a motorcycle racer gets accidentally sent back in time to cowboy days - where he romances a woman and gives her the medallion his grandmother gave him as a child. That woman ends up being his own grandmother (he is his own grandpa).
Now where did the medallion come from? Nobody ever created it, the earliest it entered the timestream was when he was sent back in time on his motorcycle; and the latest it was in the timestream was right before he was sent back. The movie was very forgettable, but the paradox of the medallion stuck with me and I was reminded of it when watching Terminator II.
Ack ... I forgot about the hand thing.
I remember Time Rider! So lame.