A drop chip is a chip that is used in the poker room for the "rake" which is the amount that the house takes out of every pot. The amount is graduated depending upon the size of the pot and has a maximum, usually $3. So, the casino/poker room issues a $3 chip that the dealer "drops" into the slot in the table that leads to the box below which holds the house share. Those chips are in the dealer's rack--when the pot reaches the maximum amount (usually $30), the dealer takes 3 $1 chips from the pot, puts them in the rack and takes out the $3 to "drop" into the box. Some places allow these drop chips to be taken away for collections, others (like the Muckleshoot near here where I often play) have very strict rules prohibiting dealers from letting them get away. Some have, however--