I've never seen a clamp like this and could use
help to explain it's function. Thanks

Made to separate the leaves in a leaf spring pack to allow squirting in some grease to reduce squeaking
People from the new world who drive new cars look at people like me and ask, "why does your old car leak so much?"
I answer back, "They ain't leaks, that's perfectly normal."
I know some of the brass era cars had wrapped leaf springs to help with lubrication, but most abandoned because as the cover failed it held in moisture & grit

I've seen a different version of that tool on another site, never one as simple as that.
https://scontent-sjc3-1.**.fbcdn.net/v/t1.0-9/38635133_10214989200876377_8655534505139896320_n.jpg?_nc_cat=106&ccb=2&_nc_sid=825194&_nc_ohc=i99Ya458GVYAX8HanZ1&_nc_ht=scontent-sjc3-1.**&oh=cd3262c221c5368c87ca4f0bf04d223a&oe=5FCD9895
Here in the 'Old World' we still make brand new cars that leak the same as the old ones!
That spring leaf separator looks like a useful tool, I may make one up from a G clamp to lubricate springs around here. Leaf springs work a lot better when lubricated it reduces the friction between the leaves, but dirt and grit can stick to the lubricant. I have a friend who used to slather grease on the leaves of his Land Rover springs when assembling them, then wrap a canvas bandage around the spring to keep the dirt out. His vehicle was more comfortable to ride in than most.