That description is brief but probably accurate. The pinfire cartridge was patented by Lefauchaux in France in 1855, and some pin fire revolvers were imported and used in the American Civil War. While never common in the U.S., where the progress was from cap and ball to rimfire to centerfire, enough were used that C.D. Leet and others made some of the cartridges. The ammunition was made in Europe at least up to WWII, but is now completely obsolete.
The gun is probably Belgium. If so, it should have a proofmark like an oval with the letters E,L,G in it. Those guns are primarily novelties but ones in good condition can bring a couple of hundred dollars.
(I don't know the intent of the seller, but don't confuse "Civil War period" with "used in the Civil War.")
Jim