This is the The Quarter Tool Bending Cutting Tool by Northwest Short Line.
Quartering is the term for setting crankpins of locomotive drivers at 90 degrees crank' apart (similar to an automobile crankshaft). Accurate quarter of all drivers in a set to the same angle (whether exactly 90 degrees or not) is critical for smooth operation of model locomotives. This tool enables quick, accurate quartering of drivers up to 1" O.D. on 1/8in or 3mm axles. The wheel is located onto the axle while the wheelset is securely held in the tool avoiding possibility of slippage. Can also be used to compare quarter of existing driver sets. A .100in clearance is required on each side of the gear. Will not fit drivers with gears wider than 1/8in (most drivers have narrower gears). Will not fit most Rivarossi drivers due to inconsistent axle diameters. Operating suggestions included. Designed by Larry Richards for your modeling pleasure. HO-S-On Includes (2) screws 1.4mm x 6mm
"This time-tested tool originally included two pins to handle some rare, unusual threads that are long since out of production. You don't need them. Use the crank pins already installed on your locomotive to set the quartering of the driver set. Using the wrong thread in your driver's crank pin hole can damage the hole's thread and possibly ruin it."