Authenticity indicator

A rapidly reversing authenticity indicator for a substrate comprising:

• a substrate having provided thereon a coating comprising a substantially colorless chromogenic material and a binder material;
• an applicator containing a developer material, the developer material comprising an organic acid of five carbons, or less a molecular weight of less than about 102, a pH of less than 3.5, and a positive vapor pressure;
• wherein the coated substrate when contacted with the developer material develops an intense color that persists less than about three minutes to provide a visual indication of authenticity of the substrate.

A rapidly reversing authenticity indicator for a substrate comprising:

• a substrate having provided thereon a coating of a substantially colorless chromogenic material and binder material,
• an applicator containing a developer material, the developer material comprising a dilute mineral acid having a molecular weight of less than about 102, and a pH of less than 3.5;
• wherein the coated substrate when contacted with the developer material develops an intense color that fades to provide a visual indication of authenticity of the substrate.

A rapidly reversing authenticity indicator for a substrate comprising:

• a substrate having provided thereon a coating comprising a substantially colorless chromogenic material and a binder material;
• an applicator containing a developer material, the developer material comprising an organic acid of five carbons or less, a molecular weight of less than about 102, and a pH of less than 2.2;
• wherein the coated substrate when contacted with the developer material develops an intense color that persists less than about three minutes to provide a visual indication of authenticity of the substrate.