Ourdan engraved the distinctive portrait of Andrew Jackson used on the 1862 United States 2c definitive. However, that was not the first time his engraving would be used. As was the usage at the time, existing dies were often used several times, on banknotes and stamps. This particular portrait by Ourdan had already been used in 1861 on a $1000 Confederate States banknote, while it can also be found on various state bank bills.
Ourdan's work for the 1870 'Busts' definitives is much more original, and engraved especially for those definitive stamps. Although the exception to that is the 3c which again was a portrait, that of Washington, which had been engraved previously for the National Bank Note Company.
The portrait of Lincoln on the 6c was an original, and documents have survived detailing the initial reaction to it and subsequent requests for alterations, before being approved. These entailed changes to both cheek (to counter the slightly morose look of the portrait) and the man's hair, which needed to be brushed forward rather than backward.
The same applied to Ourdan's engraving of the 7c, again an original engraving for this particular stamp, being the portrait of Stanton. In this instance, changes were requested especially to eye and eyebrow, in order to give the portrait 'a little haggard expression'.
Joseph Prosper Ourdan passed away in Washington DC on 10 May 1891.
You will find Joseph Prosper Ourdan's database HERE.