After doing some more research, I discovered that my typewriter was designed by Henry Dreyfuss, who also designed the Princess Phone for AT&T. His design first appeared in 1948, and had a two-tone gray matte finish. By the 1950s, his design had been rounded-off, and came in a choice of gloss colors. However, it retained the tombstone-shaped keytops, although by this time they were made of plastic.
The Quiet Deluxe was further refined by 1957, with the addition of the Twin-Pak ribbon cartridge system, and a pair of keys (1/! and =/+). The design continued until 1960, when it was completely replaced by the Futura. The futura was mechanically identical, with the exception of the addition of a key-set tabulator (on the Quiet Deluxe, tabs were manually set at the rear of the machine, under the paper support) which enabled the user to push a button to set or clear tabs. Unlike its predecessor, an unlimited number of tabs could be set.
|Royal Quiet Deluxe patent drawing (Courtesy of Google Patents)|