Praying on (almost) all cylinders
Here are the picture and a closeup of the beads, both of which I've lightened up in Photoshop so you can see them better. Click on the photo to see the closeup.
The original photo online is at Bildindex.de, the Marburg Photo Archive, which has thousands of images of art from Germany.
About 26 beads are clearly visible (not counting the ones hidden in his hands), plus a drum-shaped ending bead and tassel. The color suggests they might be wood, and at least one spherical marker bead can clearly be seen in front. We can't tell from the way they are lying whether this is a straight string or a loop -- I can only see one thread going into the top of the tassel-bead, but that could be due to the shadows. If the painter was depicting these accurately (which he may or may not have been) this might be a string of 30 (three decades) or 33 beads -- not that I can necessarily say offhand what particular devotions may go with either of those numbers.