Judging from repetitious appearances of her marital arms in the painted line-endings, the Psalter-Hours John Rylands Library Latin MS 117 probably belonged to Jeanne of Flanders (c.1272–1333), daughter of Count Robert III of Flanders and in 1288 second wife to Enguerrand IV of Coucy. Yet the line-endings also contain some 1,800 diminutive painted escutcheons, many of which refer to other members of the local nobility active during the 1280s. This study, based on an exhaustive survey of the total heraldic and codicological evidence, suggests that the majority of the extant Psalter predated the Hours and that the two parts were combined after the 1288 marriage. The ‘completed’ manuscript bears witness to major events that unfolded in and around the Coucy barony over the course of the decade. It suggests a complex relationship between Jeanne of Flanders and a lesser member of the local nobility, a certain Marien of Moÿ, who may have served as her attendant.