This is one of my all-time favorite typewriters, from its styling to its performance. I won it in a Goodwill Ebay auction on June 1, 2016, for $22.46. Since then, I've cleaned and oiled it, and got a new instruction manual for it (thanks, Greg Fudacz!) It is the smoothest running portable I've ever owned, especially for a compact. I love its imitation leather styling, and vibrant red case!
The Olivetti-Underwood Lettera 33 was introduced in 1967, to supplement Olivetti's Lettera 32 line.
I found few advertisements for the Lettera 33 (one from The Bon Marche advertising a "Lettera 33 demo., now greatly red. to clear $49.95"), Apparently, its 1970 retail price was $79.50.
Here is a list of Olivetti-Underwood dealers from the 1968 Seattle Telephone Directory