Welcome to the Forum Terry,
The numbers behind the yoke on the frame are typically S&W assembly numbers. The actual serial# is on the bottom of the grip frame between the 2 halves of the stocks. I 'll give you a link to follow to provide more detail so members can help you figure out what you have.
I'd bet 413675 is your serial number. I'm by no means an authority, but I'd put it in the mid-1920s. The authorities will be along to, perhaps, give you a better approximation.