Aargh, the above makes more sense when the first sentence reads "Talking about currency symbols I've just acquired a later Olivetti Lettera 22 (with the square keys) which has a German keyboard." 

The 'half slugs' are what is called a 'split typeface'.  Two typeface are literally sawn in half using a junior hacksaw and soldered on.  It is a very difficult job to do correctly, and one that many typewriter mechanics used to fear.  It looks like a very competent job.

Wow terrific job, I knew it was possible but never seen one such work in the flesh. IIRC there was a famous specialist in NY dubbed 'The King of Typewriters' that had an archive of tens of thousands of different typefaces and who could construct any imaginable character set at will. So, somehow he soldered them to levers - that did not make the work any  easier though.
BTW I discovered that 'Spanish' keyboard with no inverted quaotation marks but with tilded N are far from unusual in South/Central America, and Costarican, Argentinian and Uruguayan have these and also have  fraction keys. All three of them have also both pound and dollar typefaces! Bolivian, Ecuadorian and Mexican keyboards share some of these characteristics (never knew there were that much different 'Spanish' keyboards) .  If you want to check there is a nice guy  whi  patiently shared on Youtube all of 138 different optional  keyboards for Everest (Serio) machines. Olivetti surely had at least some declination of these available. Just search the 'tube' video titled :  " Identify your typewriter’s keyboard: 138 layouts of different nations "  by y-tuber  "Old Typerwriters and Calculators"  (I do not know if deep link to other services is allowed here).  The video is very informative if language layouts are your thing.