Bone or ivory calendar

Ms. calendar, perhaps of walrus ivory, incised and filled in with red and black coloring agents, made perhaps in Scandinavia, ca. 1500.
Decoration: fol. 1: Outer front cover incised with 2-register composition, on the vertical, with patterned border; at top the bound Christ brought by soldiers before a crowned, enthroned figure; at bottom Christ brought before enthroned secular judge; fol. 1v: inner front cover: horizontal composition with patterned border: Christ in Judgement at center, surrounded by groups of holy figures; fol. 2, 2v: charts with 6 small wheels inscribed with runes and sigla; fol. 3: chart with large wheel flanked by angels, below, a table of runes, on the vertical. Then follows on fols. 3v-9 the calendars for January-December, each with full-length figures carrying attributes and busts, representing saints and others commemorated in the month; fol. 9v: Chart with runes/Dominical letters/golden numbers; fol. 10, inside back cover, horizontal composition: Crowned Madonna and Child standing before throne, flanked by standing censing angels, musical figures at lower corners; flying angels flanking Madonna's head, reaching out towards crown; behind flying angels what appears to be blank shields for possible coats of arms; framed with pattern border; fol. 10v, outside back cover, vertical composition in 2 registers, upper framed on 3 sides with patterned border: the Crucifixtion with the Virgin and St. John; lower register with abstract composition composed of figures and busts and symbolic attributes, all of which occur inside in the calendar decoration. Looks like a pictographic riddle.