This is a hone I got on behalf of a friend, for whom I'm gathering the tools to start straight razor shaving. Didn't cost me much (ebay!) but postage from America took a while.
It's an excellent quality piece of kit- the carborundum company was always well respected in their time as a supplier of the finest quality abrasives. It was a bit grubby, but the dirt cleaned off when I lapped it, leaving a lovely smooth honing surface. It is quite a hard grit, so lapping won't be required for years with normal use. The grit is perfectly even, and the texture consistent throughout.
Performance- I put as good an edge on a razor with this hone as I have with the Exide, I estimate the grit to be something like 6-7K, but can't be quite sure. It puts a lovely smooth shaving edge on the razor with no effort using lather to lubricate. Only downside is there is no coarser side, so it isn't so versatile as the Exide hone. However it cuts quite fast, (faster than the fine side of the Exide) so used with no lubricant and a little pressure, minor blemishes could be honed out of a full hollow razor without much trouble.
I have to give it 10 for durability- it's still going strong after all these years, and doesn't look too delicate. The box is excellent, and quite thick, pleanty enough to protect it. Why can't packaging look like this now?
I understand that the different number Carborundum Hones (101, 102, 103) were made to slightly different recipes, but all have the same grit. Perhaps somebody who has used several could comment on any differences in performance?