I'll give this a try. I have one on a 6" Mod 29 Classic.
Top showing the 4 allen set screws used to adjust the distances.
The slot cut in the top-strap measures .410". Would imagine is cut with rounded ends, as the "wheel" is .614" in diameter.
Right Side.
Left Side
My barrel is magna-ported, just below the sight, this caused a lot of residue to get on the wheel.
The length of the base is 2.202". Width is .490". Height (of base exterior) .221". Width of sight Interior piece (which raises and lowers in the exterior base) is .340".