I suppose that postmarks for December 25th are not all that common (and certainly unheard of today) but in their time, Christmas Day postmarks do exist, as in this envelope cut square example from 1937 in Kyserike, NY:

I find it rather interesting that Kyserike, NY is a discontinued post office having been in operation only from 1904-1954. I can't even find the town on a map; the best information I have suggests it was a small hamlet in Ulster County, NY in its day and at one point had its own train station.
One would think that December 25th postmarks would be limited to large cities such as New York or Chicago, but not in this case.
Does anyone else have any December 25th postmarks they would like to share?