What is this?

[The_Yellow_Ardvark]

Had this kicking around for a while, but not sure what it is.

In Bits.

 

[ChaiLatte]

If the centre, curved section is rotated 180 degrees when in use, it looks superficially similar to a cant hook used by loggers.

Possibly an oil filter removal tool.

What size (range of) circular object(s) would it surround?

 

[Tris]

It's a bit of a guess but it looks like it may be for pulling chains, the jaws clamp on a link like pliers, the hook catches a link, then a ratchet can pull the chain up tight by closing the handles tighter as the tension increases.

 

[The_Yellow_Ardvark]

If the centre, curved section is rotated 180 degrees when in use, it looks superficially similar to a cant hook used by loggers.

Possibly an oil filter removal tool.

What size (range of) circular object(s) would it surround?

Total length of the tool is 7".

 

[Lefley]

Old brake tool my guess.

 

[eric123]

Could it be bottle opener for bottles with a crimped top

 

[budgie98]

It's what Tris said: for pulling the ends of roller chains together in order to fit the spring link.