Debate could be had about the origins or authenticity of the Blue training ball. My Theory is it is original and perhaps a very early version. I will point out t the Falcon which I got it with also had the arm riveted in. I have seen several over the years with this rivet. Was it a dad fix, an early version. ?That I am not sure.
Here is the Blue ball, black ball and a reproduction ball- or bead.
The blue and the black appear to be the same mold
The middle pix also shows the mold mark of the ship.