Consequently, Poker Chip has no effect in Chest or Dark Room.
Notes
If opening a Mega Chest yields pickups, it can spawn 1-2 Attack Flies alongside the pickups.
Synergies
Guppy's Eye: Provided that the Poker Chip is not smelted, it can be used in conjunction with the eye to open all chests with extra pickups, while dropping the chip for any chests containing flies, nullifying the downside of the trinket.
Sharp Key: Enemies killed by keys have a 50/50 chance to spawn extra pickups or an Attack Fly; the attack fly will be instantly killed by the thrown key.
Chest would contain 
Hearts, 
Coins, 
Bombs, or 
Keys and pills, cards, or runes (for 
Wooden Chests), it has a 50/50 chance to either drop extra consumables or replace all of its contents with an 
Attack Fly.
Chest or 
Dark Room.
Mega Chest yields pickups, it can spawn 1-2 Attack Flies alongside the pickups.
Guppy's Eye: Provided that the Poker Chip is not smelted, it can be used in conjunction with the eye to open all chests with extra pickups, while dropping the chip for any chests containing flies, nullifying the downside of the trinket.
Sharp Key: Enemies killed by keys have a 50/50 chance to spawn extra pickups or an 
The Binding of Isaac: Rebirth
