According to a news report that Anji, Fitz and the Eighth Doctor saw, the USS Delaware was a US Navy vessel that was once attacked 40 miles off the Libyan coast by EZ jet bombers. (PROSE: Trading Futures)
Behind the scenes[]
Although there have been several USS Delawares, none of the ones with decks were plausibly in service at the time of Trading Futures. Thus, this Delaware was a DWU-only craft.