... a very brief look at some UNDERWOOD portables
The first portables to carry the Underwood name were these little three-bank double shift machines, which were built in two basic variants from 1919/1920 through 1929.  Note that my machine on the left only has shift keys on the left side of the keyboard; the illustration shows a later unit with both "FIG" and "CAP" on the left, and "CAP" duplicated on the right.
Beginning in 1926, Underwood also produced four-bank single shift portables.  These were conventional in every way, and could be had in a variety of colors.  My machine is finished in a wonderful almost-marbled, almost woodgrain paint scheme that is unlike anything available from other manufacturers.
Underwood did practically nothing to the overall design in any major way until the machines were (finally) converted to basket shift in the 1950's.  Until then, styling changes and enclosure of the ribbons had to make do for updates.  This is my 1947 Underwood Universal. 

This machine was competitive when introduced, but was outsold handily by competing Smith-Corona and Royal machines.  One notable feature of this machine, though, is its wonderfully precise typing feel.  The feel of the standard machines seems to have been transferred to this machine, only slightly diluted.
The stylish 1950's Underwood portables are gaining in popularity, and here I'll give the details about these machines as I have them.  All of the machines you're about to see are basket-shifted.

There were two price ranges offered, which were really the same machines mechanically but with or without a host of options.  It seems as if you either got them all, or none. 
The machine you see here is my Underwood Leader.  It has practically no options; no tabulator, no ribbon color selector.  This is about as basic as you can get -- but it's still a full-sized desk portable.  Underwood did not enter the market for small, flat machines, but as we see, did offer its portable fairly stripped of anything but basic functions.
I noted the two price ranges; in Underwood machines, it appears that the top priced block didn't differ all that much.  Two different bodies were employed, and one of them seems to have had a scissors-type paper support arrangement that the other lacked.  No other notable differences are yet found.
On the left, the Underwood Universal.  On the right, the Underwood De Luxe.   Note the different shaping applied to the bodies of the machines; the Universal is squared off, like the Leader seen above; the De Luxe is much curvier.  Note the paper arms on the De Luxe, not applied to the Universal.  It seems likely that, if anything, the rounded body came earlier than the squared, but this is not proven.

Both of these have tabulator, and on both it's key-set with an identical arrangement.  The manual from which these scans came describes no differences between the two -- it covers both of these.  What is of interest in deciphering the model breakdown is the fact that the instructions came with an Underwood Ace, which is seen next.
This is the Underwood Ace.  It matches the Universal in every respect.  Note, as compared to the Leader, the fact that you can see the margin set placement through window slots cut into the paper table.  Note also the small keys on either side of the top row of character and function keys; the left one clears tab stops, and the right one sets them.
Like other manufacturers, Underwood was relabeling (or should I say re-identifying) machines through this time, so that more than one model may be applied to exactly the same typewriter.  This appears to be the case between the Universal, and this Ace.  The paperwork shows a print date of 1955, and introduces the Universal and De Luxe as new machines.
Until production ended, all Underwood did was to totally square the lines on these machines, which made them look at least roughly contemporary -- this was the 1960's.  By this time, Underwood was in real trouble.  Olivetti had bought control of the company in 1959, and in October 1963 fully merged Underwood into a new Olivetti-Underwood Corporation.  During the four-year overlap, machines appeared carrying the brand name "Underwood-Olivetti" and which were really Olivettis; after 1963, the name was changed around to "Olivetti-Underwood."  Very many machines of Olivetti design can be found carrying these names, and in the 1980's, the brand name Underwood, by itself, was briefly reintroduced.
Olivetti-Underwood Lettera 32
Olivetti-Underwood DORA
Underwood 378
There are quite a few more machines which follow this pattern, but it should be noted that all of the machines seen immediately above had nothing to do with Underwood designs, and were not built in the United States, but rather in either Italy or, much more often, in Spain.  The Underwood name lived on, but there was absolutely none of the old company behind it following the end of the 1960's.
Underwood-Olivetti Lettera 22
Olivetti-Underwood Lettera 32 and Olivetti-Underwood 21