Phone words

I recently bought a copy of Los Alamos Rolodex, a book displaying business cards from Los Alamos Nation Labs from 1967 to 1978. You can find some examples of the cards here. One of the cards in the book is for Eugene Frank, President of B & F Instruments. His card lists his phone number as (215) MErcury 9-7100 At first glance I thought the “E” in “MErcury” had been accidentally capitalized. Then I