Coti or Combo?

[mbrossar]

How do I tell the difference between a Coti on slate and a Coti combo? I have what I thought was just a Coti. I acquired a natural combo and in comparing the two, I think the first one I had was already a combo. Bummer if I bought a second stone unnecesarily (although it is a pretty stone), but I had no reference to realize it before. Any tips?

 

[Chimensch]

The blue side is purplish and the slate is black. The blue will raise a purple slurry and the slate won't. Looks like a combo to me.

 

[mbrossar]

Thanks Chimensch. Comparing the hone to my sluries, the back of the hone is definately more purple than black. I also notice (now) that the line between the coti and the back is straight on my slurries and wavy on the hone. Guess that should have been another tip. Now I need to decide which one I'm keeping.

 

[Woodash]

Check to see if there is a sharp glue joint or a natural contact (?). From what I can tell here, does not look like a glue joint....

 

[Walker]

Were did you get the stones from?

 

[danjared]

Keep in mind that not all Belgian blues are suitable as whetstones, i.e. they could have inclusions that are detrimental to an edge. But BBWs were not used as whetstones until fairly recently, so this was not a consideration for vintage coticules.