The so called "heart" symbol which you will have to admit looks nothing like a human heart or any other kind of heart, is actually a sylphium plant seed. The plant is extinct or at least nearly so. It grew in North Africa and was harvested for use as a birth control drug. Its profitability is attested to in its presence on the coins of Cyrene in North Africa. They are fairly rare and quite expensive. Here is one of my small examples with only the seed. Other coins show the whole pant which is related to celery.