(Sarah of the Clue Crew reads from a printing press at the Bureau of Engraving and Printing in Washington, D.C.)  The color of the first ink used in printing $1 bills & the part of the sheet it goes on gives us this word that dates from 1862
The advertisements for the above contract section went to press in THE .... gross 
amount of fines and deductions from postal contractors and others is over $1, ...... 
At first one printer was em- ployed; now there RAILWAY MAIL SERVICE are five.