Johannes Kaballarios, sebastos and mystikos, 13th century. Seal (Lead, 34 mm, 28.85 g, 12 h). O / A/ΓI/OC - NI/KO/ΛA/OC Saint Nicholas, nimbate, standing raising his right hand in benediction and holding book of Gospels in his left hand. Rev. +ΦVΛAΞ C[Є]/BACT૪ MVCTI/K૪ Iω KABAΛΛA/PIOV O ΠPOЄ/ΔPOC TωN / MVPωN ("The bishop of Myra is the protector of John Kaballarios, sebastos and mystikos") in six lines. Laurent, Corpus II, 127. Very fine.
As mystikos, our Konstantinos played an important administrative role in the imperial household and treasury. His seal mentions the bishop (poetically 'proedros') of Myra as his personal patron and protector. This is of course Saint Nicholas, depicted on the obverse.