Help! Anybody know what this is?

[Toolmaker51]

This sample casting, I want to use leveling a pair of jumbo outboard supports.
The ID is 2.00", star shaped nut threads on tube. Inside clamp, two thin leather strips grip when wingnuts are tightened.

But I haven't a clue what industry or trades use these, or what they're called. Tried scaffold clamp, shoring jack, adjustable * jack, cast clamp and nut...