How to show telephone numbers on letterheads - c early 1960s
The idea of a set of parenthesis surrounding the area code in a phone number dates back to the booklet above and Ladislav Sutnar’s design work for AT&T. Aflier has posted scans of this booklet which includes 15 letterheads selected by Sutnar with various options of laying out a 10 digit phone number.
(via the always excellent iso50 blog)
Also worth checking:
Sweets Catalog promo designed by Ladislav Sutnar