Count the number of characters in one inch. If there are 10, it is pica; if 12, it is elite. That is all.
The easiest way to do this does not even require you to type anything; just hold a ruler up to the paper bail or other gauge on the typewriter and note the number of tick marks there are in one inch: there will be 10 for pica and 12 for elite.

To judge from a photograph, note the highest number on one of the type gauges on the tw, and divide that by the length of the platen in inches. You will, of course, have to guess at the length of the platen, but regular ones are about 8.5-9 inches and wide carriage ones are about 11.5 inches. 100 ticks on a 10.25" platen is 10.2, so pica, e.g.

HTH
 

OlivWriter wrote:

Thank you, but there is also another difference that I notice, the "W" on some models has the central bar that goes up to the top, and other models have the central bar that stops halfway up...
What does this represent ?
 

That represents a design choice by the typeface designer, a variation for style reasons. You can see a similar, tho opposite, variation in some "M" designs. In fact, once you begin looking closely at typeface design, you will see a tremendous number of such tiny differences in all the characters (though not in every pair of characters every time). Such variations show up often in the numerals and such alpha characters as G, g, Q, f, K, R, and so on. You will see dollar signs with one vertical line and others with two.

This is the same phenomenon you see when you compare typeface designs on your computer: Times, Baskerville, Garamond, Palatino, Cambria, Bookman, Courier, Goudy, Minion, Bembo, Wiedeman among serif designs and Arial, Avant Garde, Avenir, Comic Sans, Eras, Helvetica, etc. among sans serif designs.

None of these designs have anything whatsoever to do with pica and elite in typewriters which are solely measures of pitch and not even the height of the characters.

HTH

So, if I understand correctly, Pica or Elite, it's not the style of the letter, but the space between the characters ?
And the style of the letters is completely independent of that ?

 

Along with the space between the characters...is the fact that the size of the characters differs between 10 CPI (Pica) and 12 CPI (Elite).

With my advancing ages and eye-sight, I gravitate more to Pica type fonts as they are larger in size and easier for me to see as I type.
.

skywatcher wrote:

The most common typewriter pitch in Europe I believe is 2.3 mm per character. This pitch is often referred to as European Elite and comes close to 11 cpi (clarification or correction requested).

Sky, I do not know if 11 cpi is the most common typewriter pitch in Europe. I do know that it is one of the most common pitches in the Netherlands, evenly split with 10 and 12 cpi.

In general, most European typewriter brands offered Pica and the 11 and/or 12 cpi Elite. Olympia offered the 10 and 11 cpi as their standard typefaces. Triumph/Adler did the same, but somewhere around the 60s they offered all three pitches: 10 and 12 cpi for the portables and 11 cpi for the ultra-portables. Olivetti offered 10 and 12 cpi.

Note that the above information is based on my observations and only reflect the general trend, not taking into account all brands and time periods. 

Here are some examples of European type sizes for reference:

ERIKA 

Perl (2.25 mm) 
Pica (2.6 mm)

Siegfried Junge et al, Entwicklung und Produktion von Erzeugnissen der Schreibtechnik im Kombinat Robotron (2008), p13
http://erika-electronic.de/bilder/robotronStk.pdf 

OLYMPIA 

Perl (2.3 mm)
Pica (2.6 mm) 

Olympia Schriften, Olympia Werke AG (1969), p2 
https://www.laurenzvangaalen.nl/olympia-traveller/downloads/olympia-typeface-leaflet-de.pdf