....more Underwood Portables!
Here are some further machines, and a discussion of model and body styles.
UNDERWOOD QUIET TAB (AA2639689)

Richard Polt collection

This machine represents a sub-set of the 1950's Underwood portables that have button-operated flip-up ribbon covers.  It can be seen that this is essentially a modification of the "round style" or "round shoulder" body seen on the previous page.  This machine style appears in advertisements in 1956.  This particular example is fully optioned out, with every feature ever offered on Underwood portables.
UNDERWOOD QUIET TAB ACE  (DB2748333)

Steve Lehman collection

This is another different body style, which appears in advertising from the years 1957 and 1958.  It also has a button-operated ribbon cover, and in this example the "Underwood" and "Golden Touch" brands are on the button, which is seen in larger detail, as is the labeling on the paper table.  The application of the gold background to the front panel is seemingly no accident as this appears on a wide range of "Golden Touch" machines.
UNDERWOOD STAR  (GB2917006)

David B. Davis collection

This machine has the highest serial number of any seen on this site, but confusingly does not display what has previously been thought to be the final decor variation   That variation is seen on the machine on the previous page which has a large, single "U" emblem on its front.  This machine has the Underwood / Golden Touch emblem applied directly on its flip-up cover, and is in the squared-off body style with the late flat-finish enamel paint. 

The variations in body styles are seemingly NOT in correlation with serial numbers, which will be better pointed out by the next example.
UNDERWOOD LEADER (H2344643)

David B. Davis collection

This machine is contained in the body style known previously to be roughly 1939-1949, and is carriage shifted.  However, its serial number is considerably higher than that of the very first machine displayed in our 1950's section. 

It is very likely that this machine was built right around the time that the models changed over, and was probably not built well into the 1950's as the serial number would seem to indicate.  This makes serial number reference difficult, and forces us to use advertising images as our points of reference for dating body styles (and, indeed, mechanical variations as well.)
It has been found that various models of Underwood portables are referred to in rebuilding manuals by single-letter designations, known to run from A all the way through H.  It may be true that the best way to refer to a specific body style combined with mechanical features is by the serial number prefix.  Research on this correlation is underway.