I finally gave in to the Thuringian temptation and bought a small dark blue vintage which arrived today. Mine is smooth as glass, easy to use with plain water, and seems to add a significant degree of sharpness above my previous finishers which include several coticules and the Naniwa 12k. Although these can be a bit pricey, I'm very glad I took the plunge.
As requested below, pix are now attached to reaffirm that the purchase did actually happen.