Those are called "Chinese throwing (eight) star".
You will find other sites referring to these kind of Chinese throwing (eight) star
here.
The report is about a NINJUTSU school in Tokyo. The reporter was a high schoolboy then (1997). At the school, Mr. Bright Mcgregor had taught mainly western people there.
He also had a NINJA class for little children where he used the Chinese throwing stars made of gum.
This is the simplified story of the report.