A specific type of hammer, from my work at a College in Scotland.
A: Twist Face Saw Filer Hammers (also called machinest hammers) are ideal for leveling saw plate, saw blades and band saw blades. These Twist Face Saw Filer Hammers are primarily used for Circular Saws.
So do I. I love to see if I can figure out what they are before reading the answer. Raaarrrely do I manage to get it right, but still fun trying! And, when I do get one right, well……..