This is a sigillum rex, one of the "thank-you" awards given out usually once per reign.
The text reads:
By the king ryght trusty and welbeloued. We grete yow ofte tymes wel. ffor asmuche as our right dere servant count Cadogan map Cado hath long tyme in certain matiers þat greatly concernen þe gode weele of us our Landes lordships and subgittes yeuen us gode counseil and reid, wherefor we have yeuen our assent roial that he may bere þe seal of þe kyng. Yeuen vnder our sigil at oure town of Aventiure þe iii day of January, a.s. xliii.
It was cobled together from texts 1-20 at an anthology of chancery English.
The drawings are based on one from the Snorra Edda (to acknowledge the Norse lineage of the King):
This is an image illustrating how King Gylfi of Sweden travelled to Asgard to seek the knowledge of the gods. It's from MS Delagarde 11, 14th C, on p. 24 of Jónas Kristjánsson, Handritaspegill, (Hið íslenska bókmenntafélag 1993).
The hand is an attempt at gothic littera bastarda. It passes the "arm's length" test, but that's about it.
© 2008, Sara L. Uckelman.