I found it down in my barn earlier today buried under some hay,

Let me try this again

Ring groove cleaner.

Sorry it took me so long to answer.....

Here

Thanks John

Yep, I have one just like it, belonged to my Dad.

hOpEfUlLy yur pistons never get that garbaged up to require the usage of that tool ..,

I have one too , ring groove cleaner.

I know, I know, I know...it's a ring groove cleaner.

Ring groove destroyer more like it if you aren't careful. They will remove aluminum as well.

Many of us didn't know about the carbon build up behind the rings on used high mileage motors and the need to remove that carbon before replacing the rings.
You do need to be very careful on setting the depth so you don't scrape or remove any aluminum from the pistons
I use to soak the pistons in hot soapy water for a while to help soften the carbon and then use a broken ring to scrape it out after damaging several pistons due to not setting the depth correctly
Murphy lurks and loves messing with us hot rodders

Yep, that's how we learned in the Doctor of Motors class.

https://www.orisonmarketing.com/pistonkleen.html

Caterpillar Inc. patent

https://patents.google.com/patent/US20100115721A1/en

Sample quote

]
Known carbon cleaning agents for use on disassembled engine components include
ULTRA ONE™ (sodium metasilicate, surfactants, water),
GM Goodwrench ® TOP ENGINE CLEANER (2-butoxyethanol, naphtha, 4-methyl-2-pentanol, 9-octadecendic acid) and
PRO SERIES SIMPLE GREEN® MAX AUTOMOTIVE CLEANER & DEGREASER (2-butoxyethanol, water).
Other engine cleaning agents include
acetone,
benzyl alcohol,
propylene glycol,
ethylene glycol,
Polyol esters,
n-methylpyrrolidone,
nonylphenols
and others.
Steam cleaning and cleaning with dry ice (CO2) are also known.

End quote

Sodium Metasilicate was the main active ingredient in Westley's Bleche-Wite from years past. Same chemical was used in many other WW cleaners. It was what caused the hard to breathe sensation when you sprayed it on a tire. This chemical IS NOT the same as Sodium Silicate. Sodium Silicate is used as a skin tightener in cosmetics. Sodium Metasilicate would cause skin burns when applied to the skin. Good thing pistons are more sturdy than skin.

i just soaked the pistons in carb cleaner

Around 1998 I soaked 8 used 1994 Magnum 5.9V8 used pistons in various chemicals in Folgers Coffee metal cans and the Liqui Moly “Ventril Sauber” from BMW dealerships ( means valve cleaner in German) did best,
better than Chevron Techron, Seafoam, ATF+2, Mobil One 10W-30, acetone