A user instrument for engaging in a transaction includes a graphically encoded icon having a static portion, and an intrinsic portion comprising an area of stimuli-responsive material defining a first machine-readable indicia. At least a portion of the stimuli-responsive material transforms from a first state to a second state in response to a trigger. The transformation from the first state to the second state of the portion of the stimuli-response material results in a second machine-readable indicia. The transformation of the stimuli-responsive material from the first state to the second state is semi-irreversible. The second machine-readable indicia comprises information to permit or deny the user to engage in a second transaction via the user instrument.