The Heritage description is erroneous. They realized something was wrong and added "light in weight". It's light because it's a hemidrachm. Both drachms (~2.4g) and hemidrachms (~1.2g) exist for this type. Any coin which varies significantly from one of these two standards is suspect.
My suggestion is to spend at least as much on books as you are spending on coins. I've been at this as a collector for more than 50 years now and as a professional numismatist specializing in Oriental coins for more than 20 years. I have examined thousands of Indo-Greek coins in hand. I didn't learn it all overnight. In fact I'm still learning, as we all are. As a beginner, it will serve you well to accept answers with an open mind, even those you may not like.
Edited by Kushanshah
12/21/2021 10:24 pm