Unlike a normal pilot licence which includes rating validity dates signed either by the authority or an examiner appointed on their behalf, the only indication of LAPL validity which a pilot could show is based on his/her own personal log book entries.....
....which have no independent guarantee of accuracy.
To get the "rating validity dates signed either by the authority or an examiner appointed on their behalf", doesn't the pilot simply present his logbook to the authority / examiner with "no independent guarantee of accuracy"?