For the blazon, I researched heavily in the Middle English Dictionary's examples of heraldic blazonry. I am tickled by the spelling "asure" for the more usual heraldic term "azure."
Here is the end result:
By Kenric þe kynge and Avelina þe quene to our servant Katerine atte Wyshe de la Rye, right trusti and most beloued we grete yow wel wiþ al our herte. And for asmoche as we and our counsail hier been acertained as wel be þe effecte and euidence of your werkes as be þe credible reportes and writinges maad vn to vs and to our said counsail fro tyme to tyme of þe singulier diligence & þe fulnotable and laborious seruice þat ye doon vn to þe Reaume of þe Est, & willing & praing yow alwey so to continue, for-that we do by thys lettir endowe, ablen & veste yow in perpetuite wiþ þe estate, title, and right of þe ordre of þe Pellican & ferremore do endowe, ablen & vest yow wiþ armes by lettirs patentes: Asure, a fesse argent doubly cotised golde. So that our indowment to yow may be knowen sekirly we wol ye ordeine that hit be saised in to oure handes. Yeuen at Carrillion þe .ix day of Juin, in þe fourti-sefnthe yere of þe Sociate.