The main thing is that the trio of mounting holes and the trio of holes for the trimmer blades are not symmetrically spaced. Here's a pic of the blade on top of a regular Hammond blade.
So as you can see, the central arbor hole is larger, 7/8" dia, the radius of the circle of mounting holes is slightly smaller than the Hammond, and as before the trimmers are located differently.
So I've got other blades now including a new Forrest wwI, and I thought if there is somebody out there that needs a genuine CC blade I'd offer to part with it. It is in pretty good shape although eight teeth are chipped. (marked) It is a tad bigger than 5-3/4" and has a slight boss on the back side.
I say "cost cutter" because that's how the blade looks in their manual (pdf download) - what do I know, it may fit a Morrison . . .
anyway - cheers
JW