I've seen a lot of the $2 1976 stamped/canceled date of April 13th. I noticed also, that most of the stamps are on the RIGHT side of the note.

I have come across one that has 'Dec 16th'. The stamp is on the left side and it is Christmas stamp. I couldn't find any in my searches on the web. Just wondering why it is so hard to find. And is it worth anything. It is in very good condition.