At first, I tried to break the motif down into more manageable shapes. I then used colorful frames in Substance Designer to visually connect different parts of the graph with my reference.

Due to the condition of the coin, I looked up better-preserved coins from the same era to get a better idea of its original thickness and overall shape.

As an example: The fish shape was relatively easy to recreate, with only the fin posing a minor challenge. In the end, I used a Polygon 2 node as the base for the shape.