The right-hand carriage release lever has an interesting paddle shape. Next to it, notice the vestigial remnant of a little hook/handle found on all Underwood frames, back to the model no. 1.
The ribbon covers slide away to reveal the ribbons:
This ribbon mechanism is essentially the one used on noiseless portables and later Remingtons:
The front panel easily pops off. Note that the bell is now on the right; for decades it was located on the left.
Here you can glimpse two plastic gears. The one deep inside the typewriter is part of the tabulator brake, and is a little cracked. The closer one connects to a ball chain, an unusual thing to find in a typewriter.
Underwood family reunion (older models)