when you went to the cashier box for chips.
Afterwards you changed them at the tables for regular chips.
Doing so the casino avoided that someone would steal big denominations from the cashier box.
You could not change these at the cashier box for cash.
So they were called "papier" in the casinos at the coast of Belgium.

BTW: A stick up happened in Blankenberge in the mid 90's (3 000 000 BEF) but this never got in the press.

Jo