mob spawning from spawners condition help

Hey! I am new to this so go easy on me O_o

I have not started any coding for this part yet, but I was doing research about adding the possibility for a condition for mobs that spawn from spawners not to drop a currency I am trying to add to my mod. I wish for this not to be farmed!

TLDR: Naturally spawning mobs can drop this but not ones from spawners. Is this possible? if someone can point me in the right direction that would be appareciated :P