Imagine my surprise!
I decided to re-check the serial number on my old treadle. I always went by the date on the plate. Which I found out today was a replacement part.
When I looked up the serial number on my machine I was in shock! Me who has been restoring machines for years. I got lazy with this last machine since I only did this one about 10+ years ago. (I went on a binge 35 years ago to restore machines).
Anyway when I looked up the serial number (4,324,958) I discovered this machine was much older than I thought. It came out of the factory around 1861! I checked 3 different sources. There is no letter in the serial number. I feel a bit foolish for not checking thoroughly years ago. I am glad however that I did check it now!