The Underwood Typewriter Company created the most successful typewriter designs with the #5 becoming the standard for office machines and securing Underwood's legacy.
Vintage Olivetti Underwood 21 Manual WORKING Portable - Etsy
1960s Underwood 21
1966 Olivetti-Underwood 21 on the Typewriter Database
Amazon.com: Underwood 21 Typewriter Ribbon, Black and Red, Compatible, Twin Spool : Office Products