Based on the 1962 publication date of Pale Fire, it's a leading contender for the project Nabokov might have been working on during his photo session with Carl Mydans for LIFE Magazine in 1958.

https://oac.cdlib.org/findaid/ark:/13030/kt5779r6dp/entire_text/

Estate of Carl Mydans Photography Collection<br /> Stanford University

https://site.xavier.edu/polt/typewriters/nabokov.jpeg via https://site.xavier.edu/polt/typewriters/typers.html

This photo, similar to others in the Carl Mydans series for LIFE Magazine is surely from his September 1958 photo series, though I couldn't find an original from the LIFE archive.

Nabokov, reading off of index cards in his zettelkasten, dictates to his wife Vera who is typing on what appears to be a 1949 or 1950 Henry Dreyfuss Royal Quiet De Luxe typewriter.

Notice metal strip on the back of the typewriter with small rectangular blocks. This is the Royal's tabulator set up which distinguishes the Quiet De Luxe model from the Arrow model.

The body styling of this typewriter changed in 1950 from Dreyfuss' original 1948 design. Because it's light gray it has to be from '49 or '50 as the '48 original was a black body with dark gray highlights and didn't have chrome across the front as this one does in an alternate angle.

https://images.google.com/hosted/life/2bff56953d14c9d9.html

Nabokov, reflected in a mirror off camera, dictating his writing from index cards to his wife Vera who is typing on what appears to be a 1949 or 1950 Henry Dreyfuss Royal Quiet De Luxe typewriter.

Notice the chrome on the front of the machine which is sitting in its bottom case shell.

https://images.google.com/hosted/life/c835f121c2b6ce79.html

Nabokov dictating his writing from index cards to his wife Vera who is typing on what appears to be a 1949 or 1950 Henry Dreyfuss Royal Quiet De Luxe typewriter.

https://images.google.com/hosted/life/8d0b2f02ac27973e.html

Nabokov dictating his writing from index cards to his wife Vera who is typing on what appears to be a 1949 or 1950 Henry Dreyfuss Royal Quiet De Luxe typewriter.

Alternate angle at http://images.google.com/hosted/life/81b7b3f24bbe1b3a.html

I didn't see/couldn't find this image in the Life archive, but it was obviously contemporanous to the others