ORIGINAL: AA5BY
The tool is a multi function tool part number 67537. That is the variable speed model. They also have a one speed model. Either would be suitable. IIRC, the single speed has been selling around $20. Needed will be the cutting head that is about one inch wide that I think was an accessory item.
A pic of the process.
That looks a lot like the Hobbico hinge slotting tool or am I missing something?
Howard