Do you have a piece of metal banding you could cut?
It just seems like tipping the tongue of the tool sideways, to slip it under the band, then twist it upright to nibble through it, would work well.
Perhaps you could get an idea of its purpose, through use?
As a nibbler, it does not make much sense, unless what it will nibble fits inside of the hooked end, because the hooked end cannot go in a slot which has not been nibbled yet.
I am still set on the strap/banding cutter idea. Try it! Try it!!
Tom