[Lynn Eades]

The small end runs a bearing in another shaft.
The big spline is for a sliding gear or dog, which can engage another dog either way. (lock the shaft to another shaft at the small end, or lock the shaft to the gear running on its self)
The smooth bit is where a gear runs. the little cuts are for oil.
I assume there is a hole in the splined end to bolt a flange onto , which would also have a seal track on it.
This would be a shaft from a transfer case.
The slightly shiney area of the small spline is where the bearing sits on the shaft. The bearing will be located in a housing by a circlip, and the act of bolting the flange on will stop the shaft from floating.
Are there any numbers on it?

Does that help anyone?