I've seen them. I think it is good for clamping odd shaped pieces/stock.
A handy to have clamp/vise for sure.
The way the clamping screw slides up and down in a slot, and the shouldered arrangement on the screw between the jaws, sure seem to confirm that idea. I can imagine sliding the clamping screw up/down so that it can go through the hole in the circular saw blade, with the teeth just above the jaws.
Thanks for the help guys.
The more I look at it, the more it looks to be for circular saws. I doesn't open very wide, maybe 1/2" at the most.