 In 1865 Congress required the use of " In God We Trust " on all coins large enough to bear the inscription ; in 1866 , Longacre added the motto to all silver coins larger than the dime and all gold coins larger than the three @-@ dollar piece . He also in 1867 made modifications to the design of the copper @-@ nickel five @-@ cent piece , or nickel as it was coming to be known . In 1865 , Longacre engaged British @-@ born engraver William Barber as assistant ; William H. Key was also made an assistant in 1864 and remained at the Mint past Longacre 's death . 
