The excellent instructions of the Ames section on the Underwood portables at the Classic Typewriter pages helped locate all the screws that needed to be taken out. Even so, a bit of a hassle to get all the panels off without anything being bent out of shape.
With the body-panels off, the basic, bare Underwood 'Typemaster' machine is revealed.
The mechanism looks sturdily built, if perhaps somewhat conservatively (compared to for example a Corona Speedline of similar vintage). Those side-plates of the frame look thick enough for a small truck. Most parts have been copper-plated before blackening, a nice 'quality' thing to do and excellent rust-protection.
Another thing that becomes clear however is that this particular specimen has 'issues'. The 82 year old Champion sustained some injuries, and more serious than mere missing screws. (Although those are also a challenge, finding odd-sized American vintage-type screws - in Europe...)
Of itself this first item is not problematic, the machine works fine this way, but the loose dangling end of the bell-trip (red circle) does suggest there should be something connected there. A spring? A weight?
Looking under the machine, there are already more 'anomalies'. That thin wiggly wire that actuates the line-lock does not look like a regular Underwood part (red rectangle). Also that washer between the frame and the keylever-mounting-bar that prevented the second screw looks like a suspect fix. (left red circle). Amid the rows of small thread-ends for adjusting the keylever pressure (there's a spring on top), there is one hole empty - no thread-end! (right red circle). That is worrying. There is still a spring (fortunately) and the keylever does come up again, but there should not be an empty hole there...
More to discover, but this Champion will already provide several interesting puzzles to solve! :-)