A magnetically-activatable sheet product is provided comprising a pair of laminated outer sheets between which is a magnetic layer comprising magnetically-activatable particles in a binder matrix, the outer sheets having sufficient opacity to mask the appearance of the magnetic layer; at least one of the outer sheets being provided on its outward facing surface with a coating which comprises either microcapsules containing a solution of at least one chromogenic material, or dispersed droplets containing at least one chromogenic material in a pressure-rupturable matrix, or a colour developer composition, or both microcapsules containing at least one chromogenic material and also a colour developer.
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