What is spirit? For the life of me, I could not tell you. If pressed, I'd say it's equal parts style, touch, and history. A collusion of meaning and quality that makes a thing transcend being a simple machine or a toy or picture or car, and turns it into a being.
Spirit certainly is not unique to my Olivetti's. There have been hundreds of machines that have had the same affect on writers for generations.
Woody Allen had his SM-3 since he was a kid, writing jokes for the papers. Paul Auster had his SM-9. For Jack Kerouac, there was his Hermes 3000 at least the last few years of his life, but spent most of it on an Underwood--a model from before the company was turned into a rebranding for Olivetti; he never liked the Italian company. Hemingway had his Royals, of which I think he grew more attached to as he aged. Isaac Asimov, to this day if I am not mistaken, still has his IBM Selectric I.
All of these are great machines in their own right. Many of them I own in my personal collection. None of them, with exception to the SM-9, could captivate me like the Olivetti's (especially the Lettera 32) did.
Within Olivetti, there is more than just usability and quality. When Ico Olivetti found his company, and though it would be many years before he could find the thesis statement of his grand plan, he believed that a typewriter could be all of these things: usable, affordable, beautiful. And the Lettera's are.
They endear the most die-hard love from collectors and users like Cormac McCarthy, who used his for almost his entire career. Leonard Cohen spent much of his career on a well loved Lettera 22, and Francis Ford Coppola wrote the screenplay to the Godfather on a Lettera 33.
Many writers are loyal to their machines. Many of them have an affinity for Royal, Olympia, etc. But none of them seem to have the love that comes from Olivetti users.
Finding your machine is a lot like dating, and among typers I am a bit of a whore, in that my heart belongs to many, all of them Olivetti, all of them usable, stylish, sexy. That is part of what brings me back to me time and time again.