I have a small collection of them and I find them useful to refresh an edge. I have played around with them by honing a razor to shave ready on a 4/8 Norton or the equivalent and on the second shave used a Swaty or a Frictionite, an itsapeech or a carobundum to improve the edge.

Back in the old days barbers ... and others used them with good results but now that we know about chrom ox and diamond paste or spray there are cheaper alternatives. A vintage barber hone may cost $20 to $50 or more. That is a lifetime supply of balsa wood and chrom ox.