Well, I don't know if this will contribute to the thread or not, but here's mine...a not-so-nice example of the quiver with a Western I picked up that is a bit more beefy than the 648, I think.
I really like the knife and will bring it back to life before fall. This one is still a bit small in the blade, but the grip seems to fit perfectly to the quiver.
And honestly, I think any bigger blade will cut that sheath right off the quiver because the contour of the quiver forces you to run the knife edge along the leather, I like to have the safety margin that I have with this knife.
As it is you have to be real careful to push the spine of the blade against that side of the sheath to make sure the blade doesn't contact leather and slice it to shreds.
It's not exactly the mightiest sheath for a hunting knife!
I don't know the knife model as it is not marked, but maybe the pics will help.