Hi enworb, no that's not a stupid question.
Prior to 1985 Proof coin sets were issued with the coins in the usual airtight plastic case but instead of being in a "binder" they came in two polystyrene foam cases.

You can see the "foams" just behind the coin c ASE
Prior to 1985 Proof coin sets were issued with the coins in the usual airtight plastic case but instead of being in a "binder" they came in two polystyrene foam cases.

You can see the "foams" just behind the coin c ASE






















