I think it is a plumbing tool I've seen one before

 

We had one like this in our "What's It". Let me see if I can dig it up.

I was thinking faucet seats but they were usually square or hex shaped.

Obviously a ring sizer.

Cliff may be right. Possibly a pipe rounding tool.

 

On 9/11/2020 at 9:14 AM, John Morris said:

We had one like this in our "What's It". Let me see if I can dig it up.

So here is the one I remember, but it's not quite like Cliff's, I thought it was closer to what Cliff had but it isn't.

 

Line up a clutch to the flywheel tool?

This is a radiator spud wrench, a specialized plumbing tool used for installing or removing radiator valves and nipples without damaging the internal threads. 

Function: Designed to fit into the internal lugs of radiator spuds and nipples. 

Features: Typically features a multi-step, tapered design to fit various sizes of radiator fittings. 

Material: Usually constructed from high-carbon steel or ductile iron for durability. 

Usage: Often requires a separate wrench or bar to turn the tool once inserted into the fitting. 

 

Cheers! 

MrRick

15 hours ago, MrRick said:

This is a radiator spud wrench,

Good job Rick! I did a quick Google on it and sure as heck is a spud wrench!

@Cliff will be happy mystery solved!