Martin, "There was ONE BRONZE MATRIX (with deep groove)."
Just to keep everyone with same terminology. In the above answer to Wotan your referral to 'MATRIX' here in the U.S. is called a 'model'. Some steel, brass etc. and were used to make another rubber mold when one worn out or got ruined..To keep items looking consistent this model usually didn't change but could be if needed..
A good animation on the investment cast process. Lots of work and time... This is NOT die cast process - [refer to animation in my above post]:
