What is it?

[kwbobwi]

Only markings are H-10
Spreader tool for?

 

[LS Tractor Owner]

An antique walnut cracker?

 

[DGZRT]

Old Ball joint separator

 

[Doughknob]

That would be a coil spring spreader, for inserting spacers.

 

[kwbobwi]

View attachment 749098 Old Ball joint separator

 

[kwbobwi]

Thanks, that makes sense