Olivetti Portable Typewriter Gallery -- featuring machines from Tilman Elster & Will Davis
At left, a 1937 Olivetti MP1 portable.  This was the first portable offered by the company, and was large compared to the much more common, later portables so familiar to collectors today.

We will first examine the Olivetti machines through the numbered Lettera series, followed by named versions.  The large Studio series will be featured last.
Lettera series

Our first machine is actually one of the latest, even though it has a low model number.  This 1979 Lettera 12 was introduced along with the Lettera 10 in a totally new body style.  These two models are also notable for their use of self-contained ribbon cartridges, similar to those offered by Royal and Sears-Roebuck.
At left, a 1953-built Lettera 22.  This is the machine that really opened up the market for Olivetti in portables; it was not only made in Italy, but in Spain (as Hispano-Olivetti) and England (British Olivetti.)
Following Olivetti's heavy purchase of Underwood Corporation stock in 1959, the Lettera 22 appeared in the United States carrying the Underwood-Olivetti brand name, distributed through Underwood's established dealer and sales networks.  Here is an Underwood-Olivetti Lettera 22.
In 1964, Olivetti almost completely redesigned the Lettera portable along the most modern standards of design and construction.  The Lettera 32 was the result.
In October 1963, Olivetti totally merged Underwood into a newly formed Olivetti-Underwood Corporation.  This resulted in the reversal of the double names on US machines.  Illustrating this is an Olivetti-Underwood Lettera 32.
In the years to follow, Olivetti repackaged the portable design in a bewildering array of body styles.  There are a huge number of nuanced variations; we will display a number of them here.  It should be noted that, as the small portables go, the last critical mechanical developments occurred with the development of the Lettera 32.

At left, Lettera 25.
Lettera 35
Lettera 35l
Lettera 52
Lettera DL
At right is an Olivetti Lettera 82.  This is one Lettera machine mechanically unrelated to the others; it is from a subset which was built mechanically identical to the Hermes Baby / Hermes Rocket series.  It is true that, eventually, Olivetti gained control of Paillard, and this machine is likely the result. 
Named machines.

Many Olivetti-built machines are duplicative of the Lettera or Studio series but are not labeled as such.  At left, a machine carrying only the name Achiever.  This is analagous to the late Olivetti Lettera 92 and was likely sold by Sears in the United States.
At right, the Olivetti Italia 90.  This machine is quite analagous to the Lettera 35 series.
At left, the Olivetti Tropical. This is a second machine which is based on the small Hermes design, and not the Olivetti.  Made in Brazil in the former Hermes (Paillard) facility.
At left, the Ventura.  This is analagous to the Achiever seen earlier in that no brand name whatsoever appears on the machine.  This Ventura is analagous to the more-often seen Dora, which is also seen as the Lettera 31.
At right, the same machine as the Ventura, but this time labeled as the Olivetti-Underwood Dora.
At left, another relabeling of the Lettera 92.  This machine is labeled as an Underwood 378.
Finally in our 'named' series, that most-famous Olivetti.  This is the Olivetti Valentine.
Olivetti Dora.
Olivetti Studio series.

The larger and heavier Studio series machines are actually sometimes referred to as "semi-portable," and in many ways are useful for much heavier work as might be found in small businesses or offices.

At left, the earliest model.  This is a Studio 42, made in 1947.
Olivetti Studio 44.
Above and right, two Olivetti Studio 45 machines in different colors.
At left, Studio 45S with simplified features and lower price.  Below is the later Studio 46, which changes keytops to those identical with later Lettera series machines.
Electric Portable

At left, the Olivetti Lettera 36, which was first placed on the market in 1972 and was Olivetti's first in this field.