The beads of Bishop Jakob
As with many photos from this source, these photos are black and white, not very recent, not very well lit and not very detailed. A good many of these photos are simply what the museums took when cataloguing their collections, perhaps as far back as the 1930s or 40s. It's likely that the actual photos are somewhat better than the scanned versions online, but what would really be needed for research purposes is a completely new (and much more extensive) set of photos, taken with professional lighting and a good modern camera.
There is hope, however. Any time an interesting piece is featured in an exhibit, it is likely to get at least one new picture taken, generally much better in quality than the old ones. This is particularly true when the exhibition produces a catalog. This set of beads would certainly be one of my nominees for Most Famous Rosaries of Europe, but I'm still waiting for new photos. The most recent exhibition of it that I can find is "500 Jahre Rosenkranz" in Köln (Cologne) in 1975, and that catalog seems to have used one of the old photos.
These are a bit later than the medieval beads I usually discuss in my "historical" posts. They probably date from shortly after 1600 and were left to the cathedral in Konstanz by the bishop who served there from 1604-1626.
One catalog description says they are "bone," but they are usually described as ivory, which I think is much more likely. They are very finely engraved, and ivory is far superior for this sort of thing, being both finer-grained and denser than ordinary bone.
Ivory is also a rich person's material: earlier in the Middle Ages, carved ivory was nearly as valuable as gold. Even a Renaissance piece like this is quite rare, especially as it seems to be complete and in very good condition.
All was explained when I looked at the label on the original photo from the Marburg and saw the name of the bishop who owned these beads: Jakob Fugger. No wonder he could afford them.
The Fuggers* were probably THE leading banking and mercantile family of Europe for nearly two centuries, roughly 1400 through 1600. They loaned money to emperors and Popes, and had a close relationship with the Hapsburgs, serving as personal bankers to Charles V. The later Fuggers became Counts and Princes of various territories.
Tracing which Jakob Fugger is which is a bit tricky, since the Fuggers were quite prolific, and sons in this family were routinely named for their uncles and grandfathers. In the six or seven generations during those two centuries, there were at least four previous Jakob Fuggers, along with three Ulrichs, two Georges, five Johanns and a Johann Jakob.
Bishop Jakob was a great-grand-nephew of the most famous Jakob Fugger, known as "Jakob the Rich" (d. 1525), who was probably, in relative terms, one of the richest people in Europe. He endowed almshouses in the Fuggers' home city of Augsburg that are still in existence. So even living in the 1600s, well after the Fuggers' peak of influence, Bishop Jakob must have been quite respectably wealthy.
*The temptation toward bad puns on the family name is much less, BTW, when you know that "Fugger" rhymes approximately with "sugar," and not with "mugger."
I've also discussed other ivory carvings, of a rather different sort, in this series of posts.