Torpedo Standard 2/3  serial no. 990 (mfd. 1907-1908)

Authors differ on the introduction of the first TORPEDO machine; some state that it was developed from an earlier machine known as the HASSIA.  Whatever the case, the first Torpedo machines were in production by Weil-Werke, Frankfurt Germany by 1907 and this machine, either a Model 2 or Model 3 with exceedingly low serial number was made right at this time.  The machine incorporates features already established by Remington and Underwood, but interestingly has a quickly-removable platen and carriage, and type bars are also easily removed or installed.
TORPEDO was a familiar name in typewriters for many years, entering the market within the first decade of the 20th century and continuing into the 1960's.  The firm was under partial ownership by Remington-Rand from about 1932 (the same time period that Royal bought out Orga-Werke) and this assured the company's surviving the Great Depression.  The make continued after the Second World War until shutdown in the early 1960's; production of at least one design of Torpedo machine was moved to Holland by Remington and recommenced.  All machines this page from Tilman Elster collection.
TORPEDO 4  serial 3765  (mfd. 1910-1911)

This machine is the distinctive early TORPEDO most familiar to enthusiasts, in terms of appearance; note the prominent Torpedo emblem with eagle centered above the keyboard.  Nickel-rimmed keytops have replaced the solid type used prior.
TORPEDO 5  serial no. 9305 (mfd. 1912)

This machine is the Model 5A variant - this tag may have been applied by modern collectors to describe the changes and not be original to the maker.  Some of the function controls, such as levers have been modified and relocated (ribbon selector for example.)
TORPEDO 5  serial no. 41096  (mfd. 1922)

Further changes have appeared on this Model 5B variant.  Most immediately obvious is the "opening up" of the front of the machine, albeit with retention of the front-mounted margin sets and scale.  Note also that the frame alongside the keyboard is now solid instead of open. 
TORPEDO 5  serial no. 61617  (mfd. 1922-1927)

This Model 5C types four more characters than the 5B or 5A above; two keys have been added to the top row, displacing the back-space key out to the right between the uppermost and next rows.  Like many other machines, the successful Torpedo has not been radically altered at this point even after years of production.
TORPEDO STANDARD
serial no. 492238  (mfd. 1939)

The exact point of changeover is not certain, but between the Model 5 series of the 1920's and the production of this oddly-labeled wide carriage machine, the layout of the Torpedo was radically altered to completely open up the front as on the vast majority of popular typewriters of the day.  Naturally, this forced many changes in the carriage as well so that this is practically a wholly different machine.
TORPEDO Su6  serial no. 509891  (mfd. 1950)

This machine displays the late 1930's look for Torpedo machines, carried over after the Second World War.  The machine has a clear view of the platen, as that above but is now fully enclosed by a new ribbon and type-bar cover.   Crinkle paint has replaced flat surfaced enamel. 
TORPEDO SOLITAIRE  serial 801277 (mfd. 1954)

This is the 1950's restyle of the machine, which stylistically brings the exterior in line with the vast majority of machines being made elsewhere.  Note the use of new style plastic keytops instead of the ringed type as used prior.
TORPEDO 10   serial 1068156  (mfd. 1958)

Very similar to the machine above, although equipped with conventional tabulator (instead of decimal.)  Production of all TORPEDO machines ended in 1964, and the standard was not further restyled following the dates of production of the last two machines seen here.