Rockola hammer, just a typical rebuild. I'd wipe about a pound of that grease off if it were mine. Nice weapon.
Paul, Just stumbled across that Underwood?? I really like the photos, shows good original staking which is often not visible or too light to see. My NPM has staking so light that you almost can't see it (Left over from the original flip). I guess Underwood would be one of the first to use the round bolt. Wow what a fabulous carbine!