Just picked it up again, it's definately chromed metal, it's to heavy to be plastic. That whole model select knob is a three piece unit, a notched inter plastic part then a sleeve with the model names slides over that, then the knurled chrome knob that slides down inside the notched inter plastic part.
I did wrap the barrel of the chrome top part with scotch tape and it did tighten up when It was pushed down in, but can still be pulled off with a little pulling.
So I guess it's glue chrome to plastic. I'll give it a try
Thanks
TomR