This is an iron Bishop’s cross, found in 1967 in a crypt in the cathedral in Qasr Ibrim. The Bishop that was buried was named Timotheus and the cross was a symbol of his authority.
The cross is 54 cm long. It was found over the breast of the Bishop, who had also been buried with two scrolls in Coptic and Arabic. One of the scrolls was his appointment scroll from the Coptic Patriarch which bears the date 1371 C.E. Timotheus died before he could he could take up the office, and had been buried not in his robes of office but his travelling clothes. The cross is currently in the British Museum.
The clothes that Bishop Timotheus was wearing was covered in an article by Elizabeth Crowfoot but I am unable to access it. However, a Scadian named Heather Rose Jones had read the book and created a doll based on the descriptions of the clothes. The page can be read here- http://heatherrosejones.com/digthatdoll/timotheus.html
The garb patterns have also been created by C. Mellor and can be seen on his Pinterest page- https://www.pinterest.com/unclrashid/my-sca-garb-medieval-renaissance-my-pattern-diagra/
Silk in Ancient Nubia: one road, many sources by Adams, N. PDF document through digital commons.
The Church in Africa, 1450-1950 by Adrian Hastings. Via Google books.
Medieval Nubia: A Social and Economic History by Giovanni Ruffini. Via Google books.