Число 1681 на могиле - объясняют, что в этом году было выполнено восстановление:

"Each grave is numbered, and that of Dürer is marked 649. The stone had fallen into decay, when Sandrart the painter had it renewed in 1681".





"Papers on Art, IN RELATION TO Archæology, Painting, Art-Decoration, and Art-Manufacture", LONDON,1871.
http://mirror.csclub.uwaterloo.ca/gutenberg/2/6/4/4/26449/26449-h/26449-h.htm


"ALBERT DURER A VENISE ET DANS LES PAYS-BAS", PARIS, MDCCCLXVI
https://www.gutenberg.org/files/53147/53147-h/53147-h.htm