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VINTAGE LUTZ FILE & TOOL CO. Made In USA.

Those tools were made to deburr the edges of sheet metal.  You would start at the far end of the metal and drag the V-groove along the edge of the metal towards you.

It would deburr both sides of the edge at the same time, making a tiny beveled corner on both sides of the sheet.

The handguard protects you somewhat, if the tool slips off the edge.