I imagine it would be extremely difficult if not impossible to tell from a picture, but it can't hurt to ask.
I picked this hone up for $20 at an antique store. All the guy had to say was that it was "really old". It seems to be very fine and extremely hard. I tried lapping it off and on for 2 days with wet/dry sandpaper and the progress was so painstaking I'm giving up for now until I can get a DMT.
The stone was a dark gray/blue but when I started lapping it it turned very light gray.
http://i699.photobucket.com/albums/v...2552609041.jpg
http://i699.photobucket.com/albums/v...2552609042.jpg
http://i699.photobucket.com/albums/v...2552609043.jpg
http://i699.photobucket.com/albums/v...2552609039.jpg
Any input is appreciated.