How Come I Didn't Notice This Before?

A customer was returning some strips of blood pressure medications he had bought from me earlier because there wasn't a need for it anymore. He's one of the very few people who has managed to control his BP and come off the medications.

So I was checking to see if the medications have already expired and I noticed something...

Top to bottom : Spade, Heart, Square, Asterisk, Pentagon

See those symbols next to the batch number? Has it always been there? Why didn't I notice this before? There are 2 sets of each symbol in a box of 10 strips. This is the first time I've seen something like this and I think it's quite cute. Anyone else noticed this?