I did this while attending the class "The Art of Spanish Colonial Repujado or Tin Embossing," taught by Maria Natividad. It was a lot of fun!
This was made on a sheet of aluminum with the embossing technique. A mold was not used for this but instead we created our own designs and used a sharp stick for making the lines and a blender stick for making the embossed 'popped out' areas. The black areas (called 'antiquing') were added by my instructor, Mrs. Natividad, a well-known embossing artist where I live (she used mine for the antiquing demo, else I would've added the blacks. The way she did it was brilliant).