This is very interesting. I don't quite get how you would make a mould from that particular one piece round pattern if it was solid. It would be very useful to know. All reference I came across when I was self teaching had 2 piece patterns. The ally sabers quality clearly show to me they were cast by someone who really knew their stuff.
Steven giunta: Unfortunately the video you've chosen to demonstrate this doesn't. At 1.50 he clearly 'glues' on the other half of a 2 piece master. I'll have a look on Ytube see what I can find.
Have you ever heard of a 2 piece mold?