This must be one of those replacement blocks? I'm guessing because there is a R in the circle where the casting date is. Also there is no serial #. They must've put that R there so that when the block had say a 1914 serial # but a later cast date, that would explain why. Just guessing.
I've got a replacement block in my 23
touring with no serial number. I'm going to have to look at the casting now. It's currently put away for the winter in the trailer with other things I want to keep the mice out of. I use the Coupe in the winter.