Film use indicator

Claim 1

In camera apparatus having a body to receive a canister containing a film spool defining a hollow shaft portion, the hollow shaft portion adapted to receive penetration of a spool rewind plunger carried on the camera body, the combination comprising a) said canister having a cylindrical wall and a cap defining an annular end wall with an outer side and defining an opening in registration with said hollow shaft portion to pass said plunger, the cap having a skirt engaging said cylindrical wall, b) and a frangible indicator layer extending proximate said end wall outer side, and carried by the cap, c) said layer extending over said opening and in registration with said hollow shaft portion to be penetrated by said plunger when the canister is assembled into said body, such penetration producing a puncture indicating that film carried by and rewound upon the spool has been exposed, d) said layer comprising a disc having a face attached to the cap end wall, e) the cap also defining an inner annular surface presented inwardly toward the disc periphery to protect the disc against peel off, the disc periphery extending closely adjacent said inner annular surface, inwardly of said skirt.