Abstract: The object requires a would-be user to supply an authorization code within a predetermined number of attempts, otherwise the object is invalidated. The object has at least one memory (1) in which the results of attempts at use are stored in permanent binary form. The object also includes memory write means (3) and discriminator means (9). These are arranged to distinguish between an un-interrupted sequence of said predetermined number of failed attempts (in which case the object is invalidated) and a sequence of failed attempts which is interrupted by at least one successful attempt.