Doubt the coins recovered were 'Confederate coins' in the strict sense of the term.
When the large Federal Mint at New Orleans was seized in early 1861, the South (Louisiana, then the Confederacy) took over the facility and continued production (with existing dies) to mint U.S. silver half dollars and $20 gold coins until the city fell in 1862.
With the capture of the two smaller Federal Mints at Charlotte, NC, and Dahlonrga, GA, the South also minted U.S $1 and $5 gold coins until stock ran out and operations ceased.
(Believe it would be impossible to determine whether any of these above minted U.S. coins were produced by a mint under either U.S., Southern State or Confederate control).
Only four Confederate marked silver half dollars were minted (with new dies) at New Orleans.
The Confederacy also contracted with a Philadelphia Company in early 1861 to produce a Confederate marked penny (one cent coin). Although twelve nickel sample coins were produced, the coins never reached the Confederacy.
If not an editorial error, what might have been meant here was that the coins found were 'Confederate owned coins'.