No, bluzman. Mine was in British service and probably never issued by the looks of it, maybe never even fired aside from being proved. The V*R under the crown on the lock and the Broad Arrow stamped on the top flat of the barrel indicate it was British Gov't property, and England being neutral during our Civil War made it a high crime to sell or export British Gov't arms or property to either the U.S. or C.S.
The ''Enfield'' Pattern 1853, 56, 58, and others were the Ak-47 of their day and private industry exported several hundred thousand of them to both sides from England and Belgium during the war to effectively kill each-other off. The P58 Naval and Marine Model Short Rifles, (as above and in your link) were the most effective of the Pattern having a heavier barrel with 5 groove progressive depth rifling and a 1:48 twist, they were the prize of Confederate sharpshooters.
There are some arms that saw such use that few are found today in high condition. The Enfield Short rifles are such an arm as many saw several years of hard service during the war.
Now, here's one in my collection that survived possibly several wars, a Pattern 1853 second type made in the U.S.A. by Robbins and Lawrence of Windsor Vermont for the British to use in the Crimea then returned to the U.S. or C.S. having been struck from service by England as surplus indicated by opposing Broad Arrow markings.
Note the opposing Broad Arrow stamp and deeply struck S indicating it was no longer British property
British unit markings, they were usually struck, but this one got away unscathed.