This is a brand new gear holder manufactured in Japan by Kitaco Co.
It is designed for Honda Monkey 125.
This tool is necessary when you need to remove primary drive gear.
Here are several technical informations from manufacturer:

DESCRIPTION
TOOL TO PREVENT ROTATING WHEN REMOVING & INSTALLING PRIMARY DRIVE GEAR / CLUTCH OUTER. TIGHTENS GEARS BY INSERTING THIS TOOL BETWEEN GEARS.
REMARKS
○GEAR：CHROMIUM MOLYBDENUM STEEL
※IMPACT WRENCH NOT USABLE.
GEAR MODULE 1.75 USABLE.
※PLASTIC GEAR NOT USABLE


APPLICATION
●TO PREVENT GEAR SLIPPAGE
IMPORTANT NOTICE: returns are accepted but product shall be returned inside its sealed original package.
Already mounted / used objects will be refused.