The brooch is of gilded bronze and is cast in two parts which slot together: the upper part consists of the curved bow and the square headplate, the disc and fantail foot form the lower part. The brooch is decorated all over by swirling designs of trumpet scrolls in relief within a beaded border.

There has been much discussion about this brooch over the years but it is now generally agreed that it was a product of a north of England Celtic workshop, possibly in Yorkshire, around 70 or 80 AD. Typologically, it can be seen as a development of the Continental thistle brooch, which can be found throughout the Rhineland and Gaul with some examples in Pannonia. Although parallels of the form and the decoration can be identified in Britain the Aesica brooch remains unique in bringing all the elements together in one piece of jewellery.

Modern pencils are of graphite, which was not used for writing instruments in England before the sixteenth century. But from the very late eleventh century, metallic lead was used to rule the parchment page: it superseded blind ruling (with a hard point) by the third quarter of the twelfth century and remained the commonest means of ruling until its gradual replacement by ink, including coloured inks for ornamental ruling, from the fifteenth century onwards. Lead was expensive - which was why it was so little used for roofs - and so it was worth casting this plummet with a hole at one end, for securing it, and with the name Roger, presumably its owner. A very fine late thirteenth-century plummet or lead stylus found in the Seine was lettered KAROLI SCRIPTORIS, 'of Charles the Writer'. Roger's plummet, unlike this and other plummets thought to have been used for writing, is not pointed at one end, but it is worn and perhaps once had a sharper point; and other uses (such as for a plumb-line's weight) seem unlikely.