This would be one half of the mold, I believe. The second one would fit tightly in to it, helping to create the full coin, with its' opposite face. The triangular and rectangular projections would fit in to corresponding depressions in the opposite mold.
Here are more examples of these, plus the finished coins, etc. (turn on translate)
https://sucai.redocn.com/yishuwenhua_7837639.html