Finally an attachment for Veritas® Mk.II Honing Guide that allows side clamping.
"Now even more fiddly!"
Leading edge of pictured device has a 3" rail just like leading edge of current Mk.II guide. You could imagine it is a complete replacement for the top section of the guide (that attaches to roller), but these jaws would not be sufficient to keep blades from sliding in them.
It is also worth nothing that word "temprl" is part of the url. Does this refer to temporal - meaning "of this world", or relating to time. This may be the key to understanding how it works.
Correction - I believe rail in photo is 2.75". Don't know how long it is on Mk.II.
Correction 2 - it seems jaws are angled, possibly enough to securely hold both blades with beveled sides (by bottom surface and by item being stuck into the small curve at bottom of jaws), and blades with flat sides, by pinching them on the opposite end. If I guessed what this item is, I expect a free sample.