That sporran is amazing and beautiful, but speaking purely as an artist if I were to see a current maker put a cantle of that shape over leather tooling of that shape I would say that the overall design showed a lack of integration.

I would expect an old maker to use tooling that followed the negative space within the borders of the cantle, or use a cantle the negative space of which followed the tooling of the leather.

Are you sure that that cantle and that leather originally went together?